Title of the invention: A negative electrode current collector for a lithium metal battery, a secondary battery including the same, and a method of manufacturing the negative electrode current collector for the lithium metal battery
Technical field
[One]
Mutual citation with related applications
[2]
This application claims the benefit of priority based on Korean Patent Application No. 10-2018-0017720 filed on February 13, 2018, and all contents disclosed in the documents of the Korean patent application are included as part of this specification.
[3]
[4]
Technical field
[5]
The present invention relates to a negative electrode current collector for a lithium metal battery, a battery including the same, and a method of manufacturing the negative electrode current collector, wherein the sum of S (110) and S (100) is 50% or more, and the S (110) is a ratio of the area occupied by the (110) surface of the copper based on the total area occupied by the copper on the surface of the negative electrode current collector, and S(100) is, on the surface of the negative electrode current collector It is the ratio of the area occupied by the (100) plane of the copper based on the total area occupied by the copper.
Background
[6]
Due to the rapid increase in the use of fossil fuels, the demand for the use of alternative energy or clean energy is increasing, and as part of that, the fields that are most actively studied are the fields of power generation and storage using electrochemical reactions.
[7]
Currently, a secondary battery is a representative example of an electrochemical device that uses such electrochemical energy, and its use area is gradually expanding. In recent years, as technology development and demand for portable devices such as portable computers, portable phones, and cameras increase, the demand for secondary batteries as an energy source is rapidly increasing, and among such secondary batteries, lithium secondary batteries have been studied. , Is also commercialized and widely used.
[8]
Recently, in order to achieve a high energy density, a lithium metal battery among the lithium secondary batteries has been developed. The lithium metal battery is characterized by using lithium metal as a negative electrode. In order to increase the energy density per volume or weight of the lithium metal battery, the amount of lithium metal used in the negative electrode should be reduced to an appropriate level or less. To this end, a technique of disposing a lithium metal on the negative electrode current collector when the battery is activated and driven by using the negative electrode current collector may be used.
[9]
On the other hand, when lithium metal is disposed on the negative electrode current collector, lithium metal is easily disposed unevenly, and dendrite on the resin is generated by the lithium metal, or lithium metal is added to the electrolyte due to the high reactivity of the lithium metal. And the residual moisture to form a passivation layer (solid electrolyte interphase: SEI) on the surface of the cathode. This phenomenon is accelerated when the nucleation of lithium is not smoothly performed. Since dendrite on the resin forms inert lithium that does not have electrical contact with the negative electrode current collector during battery discharge, this causes a decrease in the energy density of the negative electrode. In addition, the surface area of ​​the cathode is continuously increased by the dendritic dendrite, causing an increase and accumulation of the passivation layer. Due to this, lithium metal and electrolyte are continuously consumed, which lowers the efficiency and cycle characteristics of the lithium metal battery. Further, the separator may be destroyed by dendritic dendrite, and accordingly, battery stability is greatly degraded, such as the battery exploding.
[10]
Therefore, in order to improve the efficiency, cycle characteristics, and stability of the lithium metal battery, there is a need to develop a negative electrode current collector in which lithium nuclei can be easily formed on the surface.
Detailed description of the invention
Technical challenge
[11]
One problem to be solved by the present invention is to provide a negative electrode current collector capable of easily forming a nucleus of lithium on a surface, a lithium metal battery including the same, and a method of manufacturing the negative electrode current collector.
Means of solving the task
[12]
According to an embodiment of the present invention, there is provided a negative electrode current collector for a lithium metal battery containing copper and having a sum of S (110) and S (100) of 50% or more, and the S (110) is the negative electrode collector Based on the total area occupied by the copper on the entire surface, the ratio of the area occupied by the (110) surface of the copper, and the S(100) is based on the total area occupied by the copper on the surface of the negative electrode current collector It is the ratio of the area occupied by the (100) plane of the copper.
[13]
According to another embodiment of the present invention, preparing a preliminary negative electrode current collector including copper; And heat-treating the preliminary negative electrode current collector in a mixed gas atmosphere containing hydrogen and argon, wherein at least a part of the surface of the preliminary negative electrode current collector is made of copper. Is provided.
[14]
According to another embodiment of the present invention, a cathode; anode; A separator interposed between the anode and the cathode; And an electrolyte, wherein the negative electrode is provided with a lithium metal battery including the negative electrode current collector of the above-described embodiment.
Effects of the Invention
[15]
According to the present invention, in the negative electrode current collector for a lithium metal battery, since the sum of S (110) and S (100) is 50% or more, the formation of lithium nuclei on the surface of the negative electrode current collector can occur at a uniform and high density. have. Accordingly, since lithium metal may be uniformly formed on the negative electrode current collector, the formation of dendritic dendrite and passivation layer may be minimized. Accordingly, the efficiency, cycle characteristics, and stability of the lithium metal battery can be improved.
Brief description of the drawing
[16]
1 is a graph of potential versus capacity when plating lithium with a constant current on a copper single crystal composed of a (111) surface, a (100) surface, and a (110) surface.
[17]
2 is a SEM photograph of the negative electrode current collector (Comparative Example 1: a, Example 1: b) and an EBSD photograph of the negative electrode current collector (Comparative Example 1: c, Example 1: d).
[18]
3 is an EBSD photograph (b, c, and d) of observing the formation of lithium nuclei in the negative electrode current collector over time while driving the battery including the negative electrode current collector of Example 1 at a constant current.
[19]
4 is a graph showing the voltage versus capacity of the batteries when the batteries including each of the negative electrode current collectors of Comparative Example 1 and Example 1 are driven with a constant current.
[20]
5 is a SEM photograph showing the shape of lithium on each of the negative electrode current collectors after being driven with a specific voltage for the batteries including each of the negative electrode current collectors of Comparative Example 1 and Example 1. FIG.
[21]
6 is data comparing the density of lithium nuclei formed after driving with a constant current for batteries including each of the negative electrode current collectors of Comparative Example 1 and Example 1;
[22]
7 is a graph showing the coulomb efficiency according to the cycle of a battery including each of the negative electrode current collectors of Comparative Example 1 and Example 1;
Mode for carrying out the invention
[23]
Hereinafter, the present invention will be described in more detail to aid understanding of the present invention.
[24]
The terms or words used in the specification and claims are not to be construed as being limited to their usual or dictionary meanings, and the inventor may appropriately define the concept of terms in order to describe his own invention in the best way. It should be interpreted as a meaning and concept consistent with the technical idea of ​​the present invention based on the principle that there is.
[25]
The terms used in the present specification are only used to describe exemplary embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise.
[26]
In the present specification, terms such as "comprise", "include", or "have" are intended to designate the presence of implemented features, numbers, steps, elements, or a combination thereof, and one or more other features or It is to be understood that the possibility of the presence or addition of numbers, steps, elements, or combinations thereof is not preliminarily excluded.
[27]
[28]
The negative electrode current collector for a lithium metal battery according to an embodiment of the present invention includes copper, and the sum of S(110) and S(100) may be 50% or more. The S(110) is a ratio of the area occupied by the (110) surface of the copper based on the total area occupied by the copper on the surface of the anode current collector, and the S(100) is It is the ratio of the area occupied by the (100) plane of the copper based on the total area occupied by the copper on the surface.
[29]
[30]
At least a part of the surface of the negative electrode current collector may be made of copper. Specifically, the surface of the negative electrode current collector may be made of copper. The copper may be exposed to the outside while configuring the surface. When the lithium metal battery is driven, the copper provides a site through which lithium transferred from the positive electrode can be electrodeposited.
[31]
The copper may occupy at least a partial area of ​​the surface of the negative electrode current collector, and specifically, copper may occupy the entire area of ​​the surface of the negative electrode current collector.
[32]
The negative electrode current collector may be made of copper, and specifically, the negative electrode current collector may be made of copper foil. When the negative electrode current collector is made of copper, it is easy to manufacture a large area of ​​the negative electrode current collector. In addition, the negative electrode current collector made of copper has excellent electrochemical stability and high electrical conductivity in a lithium secondary battery. Therefore, since it can have a uniform current distribution in the negative electrode, it is very effective in realizing a large-area battery. Furthermore, the negative electrode current collector made of copper has excellent mechanical strength, so that cracks and deformations during repeated charging and discharging can be minimized.
[33]
Alternatively, the negative electrode current collector includes a substrate, and the copper may be coated on the substrate. Specifically, the copper may be in the form of covering at least a portion of the surface of the substrate, and more specifically, the copper may cover the entire surface of the substrate. When the negative electrode current collector is composed of the substrate and copper coated on the substrate, the amount of copper used can be minimized, so that production cost can be reduced. It is easy to manufacture a negative electrode current collector.
[34]
It is preferable to use a stable material that does not easily change physical properties even at high temperatures as the substrate. Specifically, the substrate may be at least one selected from the group consisting of silicon, silicon oxide, gold, stainless steel, aluminum, nickel, titanium, and silver.
[35]
The thickness of the copper coated on the substrate may be 10 nm to 5,000 nm, and specifically 10 nm to 500 nm. When the above range is satisfied, in the process of disposing copper on the substrate, the heat treatment time can be shortened, so that the process can be simplified and the electrical conductivity can be excellent.
[36]
In the negative electrode current collector, the sum of S(110) and S(100) may be 50% or more, specifically 60% or more, and more specifically 60% to 100%. Here, the S(110) is a ratio of the area occupied by the (110) surface of the copper based on the total area occupied by the copper on the surface of the negative electrode current collector, and the S(100) is the negative electrode collector It is the ratio of the area occupied by the (100) plane of the copper based on the total area occupied by the copper on the entire surface. That is, S(110) refers to the ratio of the area occupied by the (110) side of the exposed copper based on the total area of ​​copper exposed to the outside, and the S(100) is the total area of ​​copper exposed to the outside. Based on, it means the ratio of the area occupied by the (100) surface of the copper exposed to the outside. The S (110) and S (100) can be measured by the method of Electron Backscatter Diffraction (EBSD).
[37]
Compared with the (111) plane of copper, the (110) plane and the (100) plane require relatively low energy when forming lithium nuclei. This can also be confirmed through FIG. 1. 1 is a graph of potential versus capacity when plating lithium with a constant current on a copper single crystal composed of a (111) surface, a (100) surface, and a (110) surface. Referring to FIG. 1, it can be seen that the absolute value of the potential at which initial nucleation occurs is the highest in the case of a copper single crystal composed of a (111) plane, and relatively low in the case of a copper single crystal composed of a (110) plane or a (100) plane. I can.
[38]
Accordingly, in the present invention, there is a technical significance in that the (110) surface and the (100) surface of copper are positioned at a desirable level on the surface of the negative electrode current collector to easily generate lithium nuclei.
[39]
Accordingly, when the sum of S(110) and S(100) is 50% or more, lithium nuclei can easily be formed on the negative electrode current collector even with low energy, so that when the lithium metal battery is activated, lithium is used as the negative electrode collector. It can be formed in a uniform and high density primarily on the whole. Accordingly, since the formation of dendritic dendrites and passivation layers can be minimized, efficiency, cycle characteristics, and stability of the lithium metal battery can be improved. On the other hand, when the sum of S(110) and S(100) is less than 50%, there is a problem that the lithium on the resin is unevenly disposed only on a partial area of ​​the surface of the negative electrode current collector, thereby reducing the life of the battery.
[40]
The ratio of S(100) and S(110) may be 100:0 to 5:1, and specifically 20:1 to 15:1. Referring to FIG. 1, it can be seen that the absolute value of the potential at which initial lithium nucleation occurs is smaller in the case of a copper single crystal composed of a (100) plane than a copper single crystal composed of a (110) plane. However, if the S(100) is excessively increased, a problem of excessively increasing the manufacturing cost of the negative electrode current collector may occur.
[41]
Preferably, the ratio of S(100) and S(110) may be 18:1 to 17:1. When the same surface index is present in an excessively large proportion, when copper is oriented, the interference of lithium electrodeposition at the copper grain boundary intensifies, and lithium may be unevenly disposed. Therefore, the case where the ratio of the S(100) and the S(110) satisfies 18:1 to 17:1 is most preferable in terms of manufacturing cost and uniformity of lithium.
[42]
[43]
A method of manufacturing a negative electrode current collector for a lithium metal battery according to another exemplary embodiment of the present invention includes: preparing a preliminary negative electrode current collector including copper; And heat-treating the preliminary anode current collector in a mixed gas atmosphere containing hydrogen and argon, wherein at least a portion of the surface of the preliminary anode current collector may be made of copper. According to the manufacturing method, a negative electrode current collector for a lithium metal battery according to the above-described embodiment may be manufactured.
[44]
The preliminary negative electrode current collector may include copper exposed to the outside. The preliminary anode current collector may be made of copper, or the preliminary anode current collector may include a base material, and the copper may be coated on the base material. Here, the description is omitted because the description is the same as that of the above-described embodiment.
[45]
In the preliminary anode current collector, the sum of S(110) and S(100) may be less than 50%. The definitions of S(110) and S(100) are the same as described above.
[46]
The heat treatment may include introducing the preliminary negative electrode current collector into the reaction furnace, raising the internal temperature of the reaction furnace, and introducing a mixed gas containing hydrogen and argon.
[47]
The mixed gas serves to make the main surface index of copper constituting the surface of the negative electrode current collector a (100) plane, and serves to remove the copper oxide film on the surface of the negative electrode current collector.
[48]
The hydrogen may be included in 4% to 40% by weight based on the total weight of the mixed gas, and specifically 4% to 10% by weight. If the above range is satisfied, the surface index of copper can be effectively oriented so that the (100) plane can dominate in a short time even with a small amount of hydrogen content.
[49]
The inflow rate of the mixed gas may be 20 sccm to 500 sccm, and specifically 20 sccm to 100 sccm. When the above range is satisfied, the surface orientation of copper disposed on the surface of the preliminary negative electrode current collector and exposed to the outside may be uniformly adjusted as a whole.
[50]
[51]
The heat treatment may be performed at 600°C to 1,000°C, and specifically 800°C to 1,000°C. When the above range is satisfied, the ratio of the S (110) and S (100) can be adjusted to be high, and the process time can be shortened.
[52]
The heat treatment may be performed for 0.5 to 8 hours, and specifically for 0.5 to 1 hour. When the above range is satisfied, the ratio of the S (110) and S (100) can be adjusted so that a total of 50% is high, and productivity can be improved because the process time is not long.
[53]
[54]
A negative electrode according to still another embodiment of the present invention may include a negative electrode current collector. Since the negative electrode current collector is the same as the negative electrode current collector of the above-described embodiment, a description thereof will be omitted. Specifically, the negative electrode may be formed of the negative electrode current collector. In this case, initial lithium metal may be formed on the negative electrode current collector during activation of the lithium metal battery. That is, the lithium transferred from the positive electrode is not formed on the negative electrode current collector until power for activation driving is first supplied to the lithium metal battery, and according to the activation driving, the negative electrode contains lithium metal disposed on the negative electrode current collector. .
[55]
[56]
A lithium metal battery according to another embodiment of the present invention includes a negative electrode; anode; A separator interposed between the anode and the cathode; And an electrolyte. Here, since the cathode is the same as the cathode of the above-described embodiment, a description thereof will be omitted.
[57]
The positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector and including the positive electrode active material.
[58]
In the positive electrode, the positive electrode current collector is not particularly limited as long as it has conductivity without causing chemical changes to the battery, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or carbon on the surface of aluminum or stainless steel. , Nickel, titanium, silver, or the like may be used. In addition, the positive electrode current collector may generally have a thickness of 3 to 500 μm, and fine unevenness may be formed on the surface of the current collector to increase the adhesion of the positive electrode active material. For example, it can be used in various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics.
[59]
The positive electrode active material may be a commonly used positive electrode active material. Specifically, the positive electrode active material may include a layered compound such as lithium cobalt oxide (LiCoO 2 ) or lithium nickel oxide (LiNiO 2 ), or a compound substituted with one or more transition metals; Lithium iron oxides such as LiFe 3 O 4 ; Lithium manganese oxides such as formula Li 1+c1 Mn 2-c1 O 4 (0≦ c1 ≦0.33), LiMnO 3 , LiMn 2 O 3 , and LiMnO 2 ; Lithium copper oxide (Li 2 CuO 2 ); LiV 3 O 8 , V 2 O 5 , Cu 2 V Vanadium oxides such as 2 O 7 ; Formula LiNi 1-c2 M c2 O 2 (here, M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B and Ga, and satisfies 0.01≤c2≤0.3) Ni-site type lithium nickel oxide; Formula LiMn 2-c3 M c3 O 2 (where M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn and Ta, and satisfies 0.01≦c3≦0.1) or Li 2 Mn 3 MO 8 (wherein, M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn.) lithium manganese composite oxide represented by; Li in the formula may include LiMn 2 O 4 in which a part of Li is substituted with an alkaline earth metal ion, but is not limited thereto. The anode may be Li-metal.
[60]
The positive electrode active material layer may include a positive electrode conductive material and a positive electrode binder together with the positive electrode active material described above.
[61]
At this time, the positive electrode conductive material is used to impart conductivity to the electrode, and in the configured battery, as long as it does not cause chemical change and has electronic conductivity, it can be used without particular limitation. Specific examples include graphite such as natural graphite and artificial graphite; Carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; Metal powders or metal fibers such as copper, nickel, aluminum, and silver; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Alternatively, a conductive polymer such as a polyphenylene derivative may be used, and one of them alone or a mixture of two or more may be used.
[62]
[63]
In addition, the positive electrode binder serves to improve adhesion between positive electrode active material particles and adhesion between the positive electrode active material and the positive electrode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC). ), starch, hydroxypropylcellulose, recycled cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and the like, and one of them alone or a mixture of two or more may be used.
[64]
As a separator, it separates the negative electrode and the positive electrode and provides a passage for lithium ions.If it is used as a separator in a general secondary battery, it can be used without special restrictions. It is desirable. Specifically, a porous polymer film, for example, a porous polymer film made of polyolefin-based polymers such as ethylene homopolymer, propylene homopolymer, ethylene/butene copolymer, ethylene/hexene copolymer, and ethylene/methacrylate copolymer, or these A stacked structure of two or more layers of may be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of a high melting point glass fiber, polyethylene terephthalate fiber, or the like may be used. In addition, in order to secure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymer material may be used, and optionally, a single layer or a multilayer structure may be used.
[65]
The electrolyte may include, but is not limited to, an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel polymer electrolyte, a solid inorganic electrolyte, and a molten inorganic electrolyte that can be used when manufacturing a lithium secondary battery.
[66]
Specifically, the electrolyte may include a non-aqueous organic solvent and a metal salt.
[67]
Examples of the non-aqueous organic solvent include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyllolactone, 1,2-dime Oxyethane, tetrahydroxy franc, 2-methyl tetrahydrofuran, dimethylsulfoxide, 1,3-dioxolone, formamide, dimethylformamide, dioxolone, acetonitrile, nitromethane, methyl formate, Methyl acetate, phosphoric acid tryester, trimethoxy methane, dioxolone derivative, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ether, pyrofion An aprotic organic solvent such as methyl acid or ethyl propionate may be used.
[68]
Particularly, ethylene carbonate and propylene carbonate, which are cyclic carbonates among the carbonate-based organic solvents, are highly viscous organic solvents and have high dielectric constants and thus dissociate lithium salts well, so they can be preferably used.Dimethyl carbonate and diethyl carbonate and If the same low viscosity, low dielectric constant linear carbonate is mixed in an appropriate ratio and used, an electrolyte having a high electrical conductivity can be made, and thus it can be more preferably used.
[69]
The metal salt may be a lithium salt, the lithium salt is a material that is readily soluble in the non-aqueous electrolyte, for example, is in the lithium salt anion F - , Cl - , 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 3SO 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 ) 2At least one selected from the group consisting of N - can be used.
[70]
In addition to the components of the electrolyte, the electrolyte includes, for example, haloalkylene carbonate-based compounds such as difluoroethylene carbonate, pyridine, and trimethyl, for the purpose of improving battery life characteristics, suppressing reduction in battery capacity, and improving battery discharge capacity. Ethyl phosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphate triamide, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imida One or more additives, such as zolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxy ethanol, or aluminum trichloride, may be further included.
[71]
[72]
According to another embodiment of the present invention, a battery module including the lithium metal battery as a unit cell and a battery pack including the same are provided. Since the battery module and the battery pack include the lithium metal battery having high capacity, high rate characteristics and site characteristics, a medium or large size selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems It can be used as a power source for a device.
[73]
[74]
Hereinafter, a preferred embodiment is presented to aid in the understanding of the present invention, but it is obvious to those skilled in the art that various changes and modifications can be made within the scope of the present description and the scope of the technical idea. It is natural that such modifications and modifications fall within the scope of the appended claims.
[75]
[76]
Examples and Comparative Examples
[77]
[78]
Comparative Example 1: Preparation of negative electrode current collector
[79]
After preparing a commercial copper current collector (I2B, Iljin Materials) and cutting it, a cylindrical negative electrode current collector having a cross-sectional diameter of 1.6cm (16Ф) and a thickness of 20㎛ was manufactured. The sum of S(110) and S(100) of copper on the surface of the negative electrode current collector was 35.6%.
[80]
[81]
Example 1: Preparation of negative electrode current collector
[82]
Injecting the negative electrode current collector of Comparative Example 1 into a reaction furnace, and after raising the temperature of the reaction furnace to 1000 ℃, while introducing a mixed gas composed of hydrogen and argon at the temperature at the inlet rate of 21 sccm, Heat treatment was performed for 0.5 hours. Through this, a negative electrode current collector of Example 1 was manufactured. Hydrogen was included in 4% by weight based on the total weight of the mixed gas.
[83]
[84]
Experimental Example 1: S (100), S (110) confirmation
[85]
[86]
For each of the negative electrode current collectors of Example 1 and Comparative Example 1, S(100) and S(110) were confirmed. Specifically, (100) through EBSD (Bruker Quantax High Resolution equipped with a Zeiss Merlin field-emission scanning electron microscopy. The ratio of the area occupied by the (110) plane was confirmed. This method was also measured in other parts, and S(100) and S(110) were calculated through the average of a total of three results, which are shown in Table 1 and FIG. 2.
[87]
[88]
[Table 1]
S(100) (%) S(110) (%) Sum of S(100) and S(110) (%)
Comparative Example 1 16.9 18.7 35.6
Example 1 64.1 3.6 67.7
[89]
Referring to Table 1, it can be seen that by performing the heat treatment of the present invention for a commercial copper current collector, S(100) and S(110) increase, and the sum of S(100) and S(110) is 50% It was confirmed that it was abnormal.
[90]
[91]
Experimental Example 2: Evaluation of nuclear density, initial efficiency, and average Coolung efficiency of lithium
[92]
[93]
In order to check the performance of the negative electrode current collectors of Example 1 and Comparative Example 1, a half cell was manufactured in the following manner.
[94]
Each of the negative electrode current collectors in Example 1 and Comparative Example 1 was used as a positive electrode, and a 150 μm dml lithium foil was cut into 12 Φ to be used as a negative electrode. The negative electrode, the positive electrode, and the porous polyethylene separator were assembled using a stacking method, and an electrolyte solution (1,3-dioxolane (DOL)/ 1,2-dimethoxyethane (DME)) = 1 in the assembled battery. /1 (volume ratio), lithium nitrate (LiNO 3 0.2 mol)) was injected to prepare a battery.
[95]
[96]
(1) Evaluation of the nuclear density of lithium
[97]
The batteries were driven for 15 seconds in a voltage range of 0.05V, 0.1V, 0.2V, and 0.4V, respectively, and lithium metal was electrodeposited on the negative electrode current collector. Thereafter, the nuclear density of lithium metal formed on each negative electrode current collector was measured through time-current method (chronoamperometry; CA) and SH theory (see FIG. 6), and is shown in Table 2. Done. In addition, each negative electrode current collector electrodeposited with lithium metal was confirmed by SEM, and is shown in FIG. 5.
[98]
[99]
(2) Initial efficiency, average Coolung efficiency evaluation
[100]
Each of the batteries was charged and discharged to evaluate the initial efficiency and the average Coulomb efficiency, which are shown in Tables 2 and 7 below.
[101]
Meanwhile, one cycle was charged and discharged at 0.1C, and from 2 cycles to 50 cycles, charging and discharging was performed at 1C. ( Based on 1mAh/cm 2 capacity )
[102]
Discharge/Charging Conditions: CC(constant current, 1mAh/cm 2 )/ cut-offvoltage(-1V ~ 1V vs Li/Li + )
[103]
The initial efficiency (%) was derived from the results of one charge and discharge. Specifically, the initial efficiency (%) was derived by the following calculation.
[104]
Initial efficiency (%) = (discharge capacity after one discharge / capacity for one charge) × 100
[105]
The average Coulomb efficiency (%) is a value obtained by summing all of the (charging capacity/discharging capacity) × 100 of each cycle from 11 cycles to 50 cycles, and then dividing by 40.
[106]
[107]
[Table 2]
Nuclear density of lithium metal (N) Initial efficiency (%) Average coulomb efficiency (%)
Comparative Example 1 8.23 × 10 10 92.1 93.3
Example 1 4.89 × 10 11 97.7 98.3
[108]
Referring to Table 2, in the case of a battery using the improved negative electrode current collector of the present invention (the sum of S (110) and S (100) is 50% or more), the increase in the nuclear density of lithium metal on the negative electrode current collector. Able to know. Accordingly, since lithium metal can be uniformly formed on the negative electrode current collector, it can be seen that the formation of dendritic dendrites and passivation layers is minimized, thereby increasing the initial efficiency and average clogging efficiency of the battery. Referring to, it can be seen that the absolute value of the potential at which initial nucleation occurs is relatively lower in the case of using the negative electrode current collector of Example 1 than the case of using the negative electrode current collector of Comparative Example 1. Therefore, in the case of Example 1, it can be seen that the lithium nuclei are easily formed with little energy.
[109]
In addition, referring to FIG. 5, it can be seen that lithium is uniformly formed on the negative electrode current collector of Example 1 compared to Comparative Example 1. That is, it can be seen that the nucleation is uniformly formed, and the lithium electrodeposited thereafter also maintains uniformity.
[110]
[111]
Meanwhile, FIG. 3 is an EBSD picture (b, c, and d) of observing the formation of lithium nuclei in the negative electrode current collector over time while driving the battery including the negative electrode current collector of Example 1 at a constant current. Referring to this, compared to other copper crystal planes, on the (100) plane (actually red in FIGS. It can be seen that lithium is selectively plated first. Through this, it can be seen that electrochemical plating on the (100) plane of copper may occur more advantageously than other crystal planes.
Claims
[Claim 1]
A negative electrode current collector for a lithium metal battery containing copper, wherein the sum of S (110) and S (100) is 50% or more: The S (110) is based on the total area occupied by the copper on the surface of the negative electrode current collector It is the ratio of the area occupied by the (110) side of the copper, and the S(100) is an area occupied by the (100) side of the copper based on the total area occupied by the copper on the surface of the negative electrode current collector Is the ratio of.
[Claim 2]
The negative electrode current collector of claim 1, wherein the negative electrode current collector is made of the copper.
[Claim 3]
The negative electrode current collector of claim 1, wherein the negative electrode current collector includes a substrate, and the copper is coated on the substrate.
[Claim 4]
The negative electrode current collector for a lithium metal battery according to claim 3, wherein the substrate comprises at least one selected from the group consisting of silicon, silicon oxide, gold, stainless steel, aluminum, nickel, titanium, and silver.
[Claim 5]
The method according to claim 1, wherein the ratio of the S (100) and the S (110) is 100: 0 to 5: 1, the negative electrode current collector for a lithium metal battery.
[Claim 6]
Preparing a preliminary negative electrode current collector comprising copper; And heat-treating the preliminary negative electrode current collector in a mixed gas atmosphere containing hydrogen and argon, wherein at least a part of the surface of the preliminary negative electrode current collector is made of copper. .
[Claim 7]
The method of claim 6, wherein the hydrogen is contained in an amount of 4% to 40% by weight based on the total weight of the mixed gas.
[Claim 8]
The method of claim 6, wherein the inflow rate of the mixed gas is 20 sccm to 500 sccm.
[Claim 9]
The method of claim 6, wherein the heat treatment is performed at 600°C to 1,000°C.
[Claim 10]
The method of claim 6, wherein the heat treatment is performed for 0.5 to 8 hours.
[Claim 11]
The method of claim 6, wherein the preliminary negative electrode current collector is made of the copper.
[Claim 12]
The method of claim 6, wherein the preliminary negative electrode current collector includes a substrate, and the copper is coated on the substrate.
[Claim 13]
A negative electrode comprising the negative electrode current collector of any one of claims 1 to 5.
[Claim 14]
The negative electrode of claim 13, wherein the negative electrode is made of the negative electrode current collector.
[Claim 15]
The cathode of claim 13; anode; A separator interposed between the anode and the cathode; And an electrolyte; containing, a lithium metal battery.