Lithium secondary battery negative electrode, method for manufacturing the same, and lithium secondary battery using the negative electrode

Abstract

The present embodiment relates to a negative electrode of a lithium secondary battery, a method for manufacturing the negative electrode, and a lithium secondary battery comprising the negative electrode. According to one embodiment, a negative electrode of a lithium secondary battery can be provided, comprising: a current collector; and a negative electrode active material layer, which is located on at least one side of the current collector and comprises a lithium metal layer, wherein the negative electrode active material layer comprising the lithium metal layer comprises: a coating, which is located on the current collector and comprises a metal seed; and a lithium metal layer, which is located on the coating.

Description

Technical Field

[0001] The present embodiment relates to a negative electrode for a lithium secondary battery, a method for manufacturing the negative electrode, and a lithium secondary battery using the negative electrode. Background Art

[0002] In order to reduce the price of secondary batteries and improve high energy density, it has been proposed to use a lithium metal negative electrode as a negative electrode of a lithium secondary battery.

[0003] In order to form such a lithium metal negative electrode, a method of rolling a lithium foil onto a current collector is generally adopted. However, in the case of rolling, there is a problem that it is difficult to achieve a lithium metal negative electrode with a thickness of 20 μm or less.

[0004] On the other hand, in order to actually use lithium metal negative electrodes to realize secondary batteries with high energy density, a thin-film lithium metal negative electrode with a thickness of 10 to 20 μm is required. This is because if the thickness of the lithium metal negative electrode is too thin, the irreversible reaction and side reactions in the initial stage of charge and discharge will cause the life to drop sharply, and if the thickness of the lithium metal negative electrode is too thick, not only the energy density of the battery will decrease, but also the amount of lithium metal used will increase, so it is not economical.

[0005] Therefore, in order to manufacture a lithium metal anode with a suitable thickness, a method of manufacturing a lithium metal anode using an electrochemical method (ie, an electrodeposition method) has been proposed.

[0006] As described above, in the process of manufacturing a lithium metal negative electrode by electrodeposition, when a low current is applied for electrodeposition, since the electrodeposition speed is too slow, it takes a long time to obtain a lithium metal negative electrode with the required appropriate thickness as described above, and therefore it is difficult to commercialize.

[0007] In addition, when a high current is applied to increase the electrodeposition speed, the side reactions caused by the overvoltage in the early stage of electrodeposition will increase, and the protective layer on the surface of the metallic lithium negative electrode generated in the electrodeposition process will be damaged due to the high current and the resulting high voltage. Therefore, when such a negative electrode is used, the side reactions become more serious during the charge and discharge process, resulting in a decrease in the performance of the lithium secondary battery.

[0008] Therefore, there is an urgent need to develop a technology that can produce lithium metal anodes by electrodeposition and at the same time produce lithium secondary battery anodes with excellent charge and discharge characteristics. Summary of the invention

[0009] Technical issues

[0010] The present embodiment aims to provide a negative electrode for a lithium secondary battery, a method for manufacturing the negative electrode, and a lithium secondary battery comprising the negative electrode, which have excellent charge and discharge characteristics even when a high current is applied in an electrodeposition process to manufacture a negative electrode having a negative electrode active material layer comprising a lithium metal layer.

[0011] Technical Solution

[0012] According to one embodiment, a negative electrode of a lithium secondary battery comprises: a current collector; and a negative electrode active material layer, which is located on at least one side of the current collector and comprises a lithium metal layer, and the negative electrode active material layer comprising the lithium metal layer comprises: a coating, which is located on the current collector and comprises a metal seed crystal; and a lithium metal layer, which is located on the coating.

[0013] According to another embodiment, a negative electrode of a lithium secondary battery comprises: a current collector; and a negative electrode active material layer, wherein the negative electrode active material layer is located on at least one side of the current collector and comprises a lithium metal layer, and the negative electrode active material layer comprising the lithium metal layer may be a lithium metal layer containing metal seeds inside.

[0014] According to another embodiment, a method for manufacturing a negative electrode of a lithium secondary battery comprises the following steps: forming a coating on at least one side of a current collector using a coating composition containing metal seeds; positioning the current collector with the coating in a plating solution, and then positioning a lithium source at a predetermined distance from the coating; and applying an electric current between the current collector and the lithium source to form a lithium metal layer, wherein the metal seeds may be one or more selected from the group consisting of magnesium, silver, zinc, platinum, tin, silicon, aluminum, sodium, potassium, gold, bismuth, indium and germanium.

[0015] Effects of the Invention

[0016] According to this embodiment, even if an electroplating process is performed under high current conditions from the beginning to form a negative electrode active material layer, excessive nucleation of lithium particles can be prevented, and the lithium particles can be grown into a coarse structure to form a lithium metal layer containing it, and ultimately a lithium secondary battery negative electrode with a negative electrode active material layer having a uniform surface can be manufactured.

[0017] In addition, the negative electrode of the lithium secondary battery manufactured as above includes a negative electrode active material layer, and the negative electrode active material layer includes metal seed crystals, so the charge and discharge characteristics of the lithium secondary battery using the negative electrode can be significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of a method for manufacturing a negative electrode for a lithium secondary battery according to an embodiment and a negative electrode for a lithium secondary battery manufactured thereby.

[0019] Figure 2 is a schematic diagram of a negative electrode of a lithium secondary battery according to another embodiment.

[0020] Figure 3 : is a SEM picture showing the cross section of the collector on which the coating layer is formed in the process of manufacturing the negative electrode of the lithium secondary battery according to Example 1.

[0021] Figure 4a and Figure 4b The component analysis results of the current collector on which the coating layer was formed in the process of manufacturing the negative electrode of the lithium secondary battery according to Example 1 are shown.

[0022] Figure 5 It is the result of detecting the surface microstructure of the negative electrode of the lithium secondary battery formed according to the electrodeposition time.

[0023] Figure 6 The results of evaluating the charge and discharge characteristics of the lithium secondary batteries manufactured according to Example 1 and Comparative Example 1 are shown.

[0024] Figure 7 is a schematic diagram of a lithium secondary battery according to an embodiment. DETAILED DESCRIPTION

[0025] Hereinafter, embodiments of the present invention will be described in detail. However, the following embodiments are examples only, and the present invention is not limited to the embodiments described herein, and the scope of the present invention is subject to the claims.

[0026] Figure 1 Schematically shows a method for manufacturing a negative electrode for a lithium secondary battery according to one embodiment and a negative electrode for a lithium secondary battery manufactured thereby.

[0027] See also Figure 1 According to one embodiment, a negative electrode 100 for a lithium secondary battery includes a current collector 11 and a negative electrode active material layer 12 located on at least one side of the current collector 11 .

[0028] In the lithium secondary battery, the current collector 11 is used for electrical connection.

[0029] The current collector 11 may have a film shape, but is not limited thereto, and may have, for example, a mesh, foam, rod, wire, or a sheet woven from wires or fibers.

[0030] As the material of the current collector 11, a material having conductivity and limited reaction with lithium can be used. For example, as the material of the current collector 11, any one of copper, nickel, titanium, stainless steel, gold, platinum, silver, tantalum, ruthenium and alloys thereof, carbon, a conductive polymer or a composite fiber in which a conductive layer is coated on a non-conductive polymer, or a combination thereof can be used.

[0031] If the thickness of the collector 11 is thick, the weight of the battery increases, and the energy density of the battery decreases. If the thickness of the collector 11 is thin, there is a risk of overheating damage during high current operation, and the battery may be damaged by tension during the battery manufacturing process. Therefore, the thickness of the collector 11 can be 1 μm to 50 μm.

[0032] The negative electrode active material layer 12 includes: a coating layer 21 located on the current collector 11 and including metal seed crystals; and a lithium metal layer 31 located on the coating layer 21 .

[0033] As described above, when forming the negative electrode active material layer, in the case where a high current is applied to perform the electrodeposition process in order to increase the speed of electrodeposition, there is a problem that the performance of the lithium secondary battery is degraded.

[0034] However, as in the present embodiment, when the negative electrode active material layer 12 is formed into a structure having a coating 21 containing metal seeds, even if a high current is applied for the electrodeposition process, excessive generation of tiny lithium particles or destruction of the surface protective layer coating of the lithium metal layer generated in the electrodeposition process can be prevented.

[0035] More specifically, since the negative electrode active material layer of this embodiment has a coating layer containing metal seeds, when a high current is applied in the electrodeposition process to form a lithium metal layer on the coating layer, the initially generated lithium particles can be guided to grow smoothly to form coarsely structured particles, while the lithium metal layer has a uniform surface, ultimately giving the negative electrode active material layer a uniform surface.

[0036] Therefore, the performance of the lithium secondary battery using the negative electrode according to the present embodiment can be significantly improved, and specifically the charge-discharge characteristics can be significantly improved. In addition, when a high current is applied to quickly carry out the electrodeposition process, a lithium secondary battery negative electrode with high performance can also be manufactured, so the productivity of the lithium secondary battery negative electrode can also be significantly improved.

[0037] For example, the metal seed crystal may be one or more selected from the group consisting of magnesium, silver, zinc, platinum, tin, silicon, aluminum, sodium, potassium, gold, bismuth, indium, and germanium, but is not limited thereto.

[0038] In this embodiment, the coating layer includes metal seeds. When the coating layer includes metal seeds, electrons are smoothly supplied from the current collector due to the inclusion of metal seeds with high electron conductivity, and lithium ions are reduced, which has the advantage of facilitating the electrodeposition of the lithium metal layer.

[0039] However, when the particles contained in the coating are in the form of metal oxides, the electron conductivity is lower than that of the present embodiment, and electrons cannot be smoothly supplied from the current collector. Therefore, the coating containing metal oxides in the electrodeposition process will instead act as a resistance layer. In this case, there is a problem that the electrodeposition of the lithium metal layer is difficult to carry out.

[0040] In addition, as in the present embodiment, when a lithium metal layer is formed on a coating layer containing metal seeds, since the nucleation free energy can be reduced in the initial nucleation stage of lithium particles in the electrodeposition process, a lithium metal layer with a coarse particle structure can be formed even under high current and overvoltage conditions.

[0041] In the negative electrode of the present embodiment, the thickness of the coating may be 0.01 μm to 10 μm, more specifically 100 nm to 500 nm. When the thickness of the coating satisfies the range, uniform electrodeposition of coarse lithium particles can be achieved, which is an effect obtained by including the above-mentioned metal seeds. In contrast, when the thickness of the coating containing the metal seeds is too thin, as the coating area expands, it is easy to produce uneven local coating thickness, and eventually there is a defect of uneven size of the generated lithium particles. On the other hand, when the thickness of the coating is too thick, there is a problem of increased weight and volume leading to a decrease in battery energy density. However, for such a coating thickness, it can be variably adjusted according to the design of the lithium secondary battery structure.

[0042] The thickness of the negative electrode active material layer 12 may be 1 μm to 100 μm, and more specifically, may be 5 μm to 30 μm.

[0043] When the thickness of the negative electrode active material layer 12 is too thick, in the case where the negative electrode of the present embodiment is applied to a lithium secondary battery, the weight and volume of the battery will increase, resulting in a problem of reduced energy density. In addition, when forming the negative electrode active material layer 12, the time and cost of the electrodeposition process increase in proportion to the thickness, so the thickness of the negative electrode active material layer 12 is preferably 100 μm or less.

[0044] In addition, when the thickness of the negative electrode active material layer 12 is too thin, when the negative electrode of the present embodiment is applied to a lithium secondary battery, there is a problem of reduced charge and discharge life of the battery. Specifically, in general, during the charge and discharge process of the battery, the lithium in the battery is gradually consumed due to the side reaction of the lithium contained in the negative electrode active material layer with the electrolyte, and thus the battery capacity will decrease. However, if the thickness of the negative electrode active material layer 12 is thin, the amount of lithium held that can replenish the lithium consumed during the charge and discharge process is reduced, and thus the charge and discharge life of the battery will be reduced. Therefore, the thickness of the negative electrode active material layer 12 is preferably greater than 1 μm.

[0045] On the other hand, although not shown in the drawings, the negative electrode active material layer of this embodiment may further include a coating film, which is located on the surface of the negative electrode active material layer.

[0046] The coating is formed by the reaction between the lithium metal of the electrodeposited lithium source and the plating solution during the manufacturing process of the negative electrode active material layer 12. The thickness, composition, characteristics, etc. of the coating can be controlled by adjusting the composition of the plating solution used and the conditions of the electrodeposition process.

[0047] For example, the thickness of the coating may be 2 nm to 2 μm, and more specifically, may be 10 nm to 500 nm.

[0048] If the thickness of the coating on the surface of the negative electrode active material layer 12 is too thick, the lithium ion conductivity is reduced, the interface resistance is increased, and when applied to a battery, the charge and discharge characteristics may be reduced. In addition, if the thickness of the coating is too thin, the coating is easy to fall off during the application of the lithium metal negative electrode according to the embodiment to the battery.

[0049] Therefore, the coating film is preferably formed uniformly and densely on the entire surface of the negative electrode active material layer 12 with a relatively thin thickness within the range satisfying the above thickness.

[0050] At this time, the coating may include one or more substances selected from the group consisting of Li-NCHO-based ionic compounds, Li-PCHO-based ionic compounds, and LiF.

[0051] Figure 2 FIG. 2 schematically shows a negative electrode of a lithium secondary battery according to another embodiment.

[0052] See also Figure 2 According to another embodiment, a negative electrode 100 of a lithium secondary battery includes: a current collector 11 ; and a negative electrode active material layer 12 , which is located on at least one side of the current collector 11 and includes a lithium metal layer 31 .

[0053] At this time, the negative electrode active material layer 12 including the lithium metal layer 31 is a lithium metal layer 31 including the metal seed crystals 22 therein.

[0054] For example, the metal seed crystal 22 may be one or more selected from the group consisting of magnesium, silver, zinc, platinum, tin, silicon, aluminum, sodium, potassium, gold, bismuth, indium, and germanium, but is not limited thereto.

[0055] In the present embodiment, the negative electrode active material layer 12 is in the form of a lithium metal layer 31 containing metal seeds 22. As described above, when the negative electrode active material layer is formed in the form of a lithium metal layer 31 containing metal seeds 22, since the nucleation free energy can be reduced at the initial nucleation stage of lithium particles in the electrodeposition process, a lithium metal layer having a coarse particle structure can be formed even under high current and overvoltage conditions.

[0056] In this embodiment, the thickness of the negative electrode active material layer may be 1 μm to 100 μm, more specifically 5 μm to 30 μm. In this embodiment, when the negative electrode active material layer 12 meets the thickness range, the advantages are that the charge and discharge life of the battery can be improved, the energy density of the battery can be maximized, and the time and cost of the electrodeposition process when forming the negative electrode active material layer can be reduced as much as possible.

[0057] In this embodiment, the metal seed crystals included in the lithium metal layer may be in a form of alloying with the lithium in the lithium metal layer.

[0058] As described above, when the negative electrode active material layer (i.e., the lithium metal layer) contains metal seeds alloyed with lithium, the alloy reversibly changes to metal seeds during discharge, so that lithium ions are easily alloyed during recharging. In other words, the role of the seeds can be repeatedly played during the charge and discharge process, so that the dendritic growth of lithium can be prevented, which has the advantage of improving the battery life.

[0059] On the other hand, although Figure 2 Although not shown in the figure, the negative electrode active material layer of this embodiment may further include a coating film, which is located on the surface of the negative electrode active material layer.

[0060] The coating is the same as described above in the negative electrode of the lithium secondary battery according to one embodiment, and thus will not be described in detail.

[0061] According to one embodiment, a method for manufacturing a lithium secondary battery comprises the following steps: forming a coating on at least one side of a current collector using a coating composition containing metal seeds; positioning the current collector with the coating in a plating solution, and then positioning a lithium source at a predetermined distance from the coating; and applying a current between the current collector and the lithium source to form a lithium metal layer.

[0062] First, a coating is formed on at least one side of a current collector using a coating composition containing metal seeds.

[0063] At this time, for example, the metal seed crystal may be one or more selected from the group consisting of magnesium, silver, zinc, platinum, tin, silicon, aluminum, sodium, potassium, gold, bismuth, indium, and germanium, but is not limited thereto.

[0064] Furthermore, for example, the coating may be formed by at least one of sputtering, electroplating and electroless plating, electron beam deposition, and thermal vapor deposition.

[0065] On the other hand, in the step of forming a coating layer, the coating layer formed on at least one side of the current collector may have a thickness of 0.01 μm to 10 μm, and more specifically, 100 nm to 500 nm.

[0066] When the coating thickness meets the above range, the negative electrode of the lithium secondary battery according to one embodiment can be made into a negative electrode having the following characteristics: Figure 1 The structure of the negative electrode 100 of a lithium secondary battery is shown.

[0067] Therefore, in the subsequent process performed after the coating formation step, the step of forming the lithium metal layer can make the lithium metal layer located on the coating formed on at least one side of the collector to form a negative electrode active material layer having multiple layers.

[0068] Alternatively, in the coating layer forming step, the coating layer formed on at least one side of the current collector may have a thickness of 10 nm to 100 nm.

[0069] When the coating thickness meets the above range, the negative electrode of the lithium secondary battery according to another embodiment can be made into a negative electrode having the following characteristics: Figure 2 The structure of the negative electrode 100 of a lithium secondary battery is shown.

[0070] Therefore, in the subsequent process performed after the coating formation step, the step of forming a lithium metal layer can cause the metal seeds contained in the coating formed on at least one side of the collector to alloy with the lithium in the lithium metal layer and diffuse into the interior to form a single negative electrode active material layer.

[0071] On the other hand, after the coating formation step, the collector formed with the coating is positioned in a plating solution, a lithium source is then positioned at a predetermined distance from the coating; and a current is applied between the collector and the lithium source to form a lithium metal layer.

[0072] See also Figure 1 , the steps of forming the lithium metal layer are described in more detail.

[0073] First, the current collector 11 formed with the coating layer 20 is positioned in the plating solution 40 , and then the lithium source 30 is positioned at a predetermined interval from the coating layer 20 .

[0074] For example, as the lithium source 30 , lithium metal, lithium alloy, a foil of the lithium metal or lithium alloy pressed on a current collector, a plating solution in which a lithium salt is dissolved, or the like can be used.

[0075] The current collector 11 is the same as that described above, and thus will not be described in detail.

[0076] The plating solution 40 may be prepared by dissolving a lithium salt in a non-aqueous solvent.

[0077] More specifically, the lithium salt may be LiCl, LiBr, LiI, LiCO3, LiNO3, LiFSI, LiTFSI, LiBF4, LiPF6, LiAsF6, LiClO4, LiN(SO2CF3)2, LiBOB or a combination thereof. The concentration of the lithium salt may be 0.1 to 3.0 M based on the total electrolyte.

[0078] More specifically, in the present embodiment, the plating solution is characterized in that, as at least one of the lithium salt and the non-aqueous solvent, the plating solution contains a nitrogen-based compound.

[0079] For example, the nitrogen-based compound may include one or more selected from the group consisting of lithium nitrate, lithium bis fluorosulfonyl imide, lithium bistrifluoromethane sulfonimide, e-caprolactam, N-methyl-e-caprolactam, triethylamine and tributylamin.

[0080] Among the nitrogen-based compounds, at least one of lithium nitrate, lithium bis fluorosulfonyl imide, and lithium bistrifluoromethane sulfonimide may be used as the lithium salt.

[0081] Among the nitrogen-based compounds, at least one of e-caprolactam, N-methyl-e-caprolactam, triethylamine, and tributylamin may be used as the non-aqueous solvent.

[0082] On the other hand, for the plating solution, a general non-aqueous solvent may be further added as a solvent in consideration of the viscosity of the plating solution, etc. If the viscosity of the plating solution is too high, the mobility of lithium ions decreases, and the ion conductivity of the plating solution decreases, so the time required for the electrodeposition process increases, resulting in reduced productivity.

[0083] For example, the solvent may include ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, tetrahydrofuran, 1,3-dioxolane, 1,4-dimethoxyethane, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, tetrahydrofuran, 1,3-dioxolane, 1,4-dimethoxyethane, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, tetrahydrofuran, 1,3-dioxolane, 1,4-dimethoxyethane, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, tetrahydrofuran, diethylene glycol dimethyl ether ... 1,4-Dioxane and 1,3,5-trioxane One or more selected from the group consisting of alkanes (1,3,5-trioxane).

[0084] In the step of applying current to form a lithium metal layer on at least one side of the current collector, the current density of the applied current may be 0.1 mA / cm 2 Up to 100mA / cm 2 , more specifically 0.2 mA / cm 2 Up to 50mA / cm 2 , 5mA / cm 2 Up to 30mA / cm 2 or 7mA / cm 2 Up to 25mA / cm 2 .

[0085] In addition, the time for applying the current may be 0.05 hours to 50 hours, and more specifically, may be 0.25 hours to 25 hours.

[0086] As described above, in this embodiment, excessive generation of tiny lithium particles is prevented under high current conditions, and the lithium particles generated in the early stage are guided to grow smoothly, so that a negative electrode having a negative electrode active material layer including a lithium metal layer with a coarse particle structure can be manufactured. In addition, the negative electrode active material layer manufactured in this way also has excellent surface uniformity. Therefore, when the negative electrode manufactured according to this embodiment is used, the charge and discharge characteristics of the lithium secondary battery can be significantly improved.

[0087] A lithium secondary battery according to one embodiment includes a positive electrode, a negative electrode, and an electrolyte located between the positive electrode and the negative electrode.

[0088] Figure 7Schematically shows the structure of a lithium secondary battery according to one embodiment.

[0089] See also Figure 7 The lithium secondary battery 200 of the present embodiment may include an electrode assembly including a positive electrode 70 , a negative electrode 100 , and a separator 90 disposed between the positive electrode 70 and the negative electrode 100 .

[0090] This electrode assembly is bent or folded and placed in a battery container 95 .

[0091] Then, the electrolyte 80 is injected into the battery container 95 and sealed, thereby completing the lithium secondary battery 200. At this time, the battery container 95 may have a cylindrical shape, a square shape, a pouch shape, a coin shape, or the like.

[0092] For convenience, Figure 7 1 and 2 show a negative electrode according to an embodiment as the negative electrode 100 . However, the negative electrode of the lithium secondary battery according to the aforementioned embodiments can be used as the negative electrode.

[0093] The positive electrode 70 may include a positive electrode active material layer and a positive electrode current collector.

[0094] For example, the positive electrode active material layer may include a Li compound including at least one metal selected from Ni, Co, Mn, Al, Cr, Fe, Mg, Sr, V, La, Ce and at least one non-metallic element selected from the group consisting of O, F, S, P and combinations thereof. The positive electrode active material layer may include active material particles having a size of about 0.01 μm to 200 μm, which may be appropriately selected according to the desired characteristics of the battery.

[0095] According to circumstances, a conductive material may be added to the positive electrode active material layer.

[0096] For example, the conductive material may be carbon black and ultrafine graphite particles, fine carbon such as acetylene black, nano metal particle slurry, etc., but is not limited thereto.

[0097] The positive electrode current collector plays a role of supporting the positive electrode active material layer. As the positive electrode current collector, for example, aluminum foil, nickel foil, or a combination thereof may be used, but is not limited thereto.

[0098] As the electrolyte 80 filled in the lithium secondary battery 200 , a non-aqueous electrolyte, a solid electrolyte, or the like can be used.

[0099] For example, the non-aqueous electrolyte may include lithium salts such as lithium hexafluorophosphate and lithium perchlorate and solvents such as ethylene carbonate, propylene carbonate, and butylene carbonate. In addition, for example, the solid electrolyte may use a gel polymer electrolyte in which an electrolyte is impregnated in a polymer electrolyte such as polyethylene oxide and polyacrylonitrile, or an inorganic solid electrolyte such as LiI and Li3N.

[0100] The separator 90 is used to isolate the positive electrode and the negative electrode and provide a migration channel for lithium ions, and can be used for lithium secondary batteries. That is, a separator with low ion migration resistance to the electrolyte and excellent electrolyte wetting ability can be used. For example, the separator can be selected from glass fiber, polyester, polyethylene, polypropylene, polytetrafluoroethylene or a combination thereof, and can be in the form of a non-woven fabric or a fabric. On the other hand, when a solid electrolyte is used as the electrolyte 80, the solid electrolyte can also be used as the separator 90.

[0101] Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples only and the present invention is not limited thereto. The scope of the present invention is subject to the claims.

[0102] (Example 1)

[0103] Through Figure 1 The process shown manufactures the negative electrode of the lithium secondary battery according to Example 1.

[0104] First, a magnesium-containing coating layer 20 having a thickness of about 250 nm is formed on one side of a copper current collector 11 having a thickness of 10 μm by a sputtering method.

[0105] The current collector 11 formed with the magnesium-containing coating layer 20 as described above is positioned in the plating solution 40, and then the lithium source 30 is positioned at a predetermined interval from the coating layer.

[0106] For the plating solution, based on 100 wt % of the plating solution, 40 wt % and 10 wt % of lithium bis(fluorosulfonyl)imide (LiFSI) and lithium nitrate (Lithium nitrate) are added respectively, and then about 19 wt % of the fluorine-based compound fluoroethylene carbonate (Fluoroethylene carbonate, FEC) is added based on 100 wt % of the plating solution to manufacture the plating solution.

[0107] In addition, as the lithium source 30 , a lithium metal plate having a purity of 99.9% or more and a thickness of 500 μm was pressed onto a copper current collector plate (copper plate) and used.

[0108] The lithium source 30 and the collector 11 are stacked in a plating solution 40 in an electrically insulating state, and then the lithium source 30 and the collector 11 are used as (+) and (-) electrodes respectively, and current is applied using a power supply device. This method forms a lithium metal layer 31 located on the coating 21.

[0109] At this time, the average current density of the process is set to 8 mA / cm 2 , the process time was set to about 0.6 hours to manufacture the negative electrode 100 having the negative electrode active material layer 12 having a thickness of about 20 μm.

[0110] (Comparative Example 1)

[0111] A negative electrode having a negative electrode active material layer formed thereon was manufactured in the same manner as in Example 1 except that a copper current collector having a thickness of 10 μm and no external coating layer was used instead of the current collector having the magnesium-containing coating layer formed thereon.

[0112] (Experimental Example 1)

[0113] In Example 1, the cross-sectional structure and composition of the current collector formed with the coating layer were examined, and the results are shown in FIG. Figure 3 and Figure 4a , Figure 4b middle.

[0114] That is to say, Figure 3 This is a SEM image of a cross section of a current collector with a coating formed thereon. Figure 4a and Figure 4b The component analysis results of the current collector on which the coating layer was formed are shown.

[0115] For component analysis, after processing the cross section with a focused ion beam, energy dispersive X-ray spectroscopy was used to perform component analysis.

[0116] See also Figure 3 , Figure 4a , Figure 4b , it can be confirmed that a magnesium coating is uniformly formed on the surface of the collector.

[0117] (Experimental Example 2)

[0118] The negative electrode active material layer was formed by the same method as in Example 1 and Comparative Example 1, but the electrodeposition process time was shortened to 1 minute, 2 minutes, and 3 minutes to detect the surface microstructure of the negative electrode active material layer formed in the early stage of the electrodeposition process. The microstructure was detected by scanning electron microscopy after processing the cross section with a focused ion beam, and the results are shown in Figure 5 middle.

[0119] This is to confirm the microstructure of lithium particles at the early stages of the electrodeposition process.

[0120] See also Figure 5 It can be seen that in the very short period of time at the beginning of the electrodeposition process, there are also great differences in the nucleation and particle growth behaviors of the initial lithium particles.

[0121] That is, as described in Comparative Example 1, under high current conditions, when a negative electrode active material layer including a lithium metal layer is formed on a current collector without a coating, tiny particles are excessively generated over the entire area of ​​the surface of the negative electrode active material layer. The particles grow slowly over time, but the particle size after growth is also relatively small.

[0122] In contrast, as shown in Example 1, after forming a magnesium-containing coating, when a lithium metal layer is formed on the coating to manufacture a negative electrode active material layer, although the number of generated particles is small, lithium grows significantly even in a short time, thereby having a coarse particle structure.

[0123] Therefore, as described in this embodiment, when an electrodeposition process for forming a negative electrode active material layer is implemented, if the negative electrode active material layer is manufactured to contain metal seeds that are easily alloyed with lithium, excessive nucleation can be prevented even in a high-speed electrodeposition process that requires application of a high current at the beginning, thereby preventing the specific surface area of ​​the negative electrode active material from increasing.

[0124] Therefore, the side reaction between the lithium secondary battery and the electrolyte during charge and discharge can be reduced, and finally the charge and discharge characteristics can be significantly improved.

[0125] (Experimental Example 3)

[0126] The negative electrode of the lithium secondary battery manufactured according to Example 1 and Comparative Example 1 was used to prepare a Figure 7 A lithium secondary battery (2032-type coin half cell) with the structure shown was prepared, and the charge and discharge characteristics were evaluated.

[0127] Specifically, for the positive electrode, a positive electrode active material slurry containing LiCoO2 (99 wt%) active material, a conductive material and a binder is used to prepare a positive electrode active material layer, which is laminated on one side of the current collector (aluminum foil). At this time, the capacity per unit area of ​​the positive electrode is 3.1 mAh / cm 2 , which is equivalent to the positive electrode capacity level of currently commercialized lithium secondary batteries (using graphite negative electrodes).

[0128] As the electrolyte, a mixed solvent (volume ratio of 3:7) of ethylene carbonate and ethyl methyl carbonate in which 1 M of LiPF6 was dissolved was used.

[0129] The separator used was a 2400 model product from Celgard made of polypropylene, and the battery container used a 2032 model coin cell product from Hohsen.

[0130] The charge and discharge performance of the lithium secondary battery produced by the above method was evaluated as follows.

[0131] The charging step is to charge to 4.25V with a constant current of 0.2C, and then charge from 4.25V to 0.05C with static electricity. The discharging step is to discharge to 3.0V with a constant current of 0.5C.

[0132] The results of evaluating the charge and discharge performance of lithium secondary batteries are shown in Figure 6 and Table 1 below.

[0133]

Table 1

[0134] Classification Charge and discharge life (number of times) Comparative Example 1 6 Example 1 33

[0135] See also Figure 6 As can be seen from Table 1, the charge and discharge life of the lithium secondary battery using the lithium secondary battery negative electrode manufactured according to Example 1 is significantly better than that of the lithium secondary battery using the lithium secondary battery negative electrode manufactured according to Comparative Example 1.

[0136] This is because, by adopting a negative electrode having a negative electrode active material layer containing metal seeds as in the present embodiment, the surface area of ​​the negative electrode in contact with the electrolyte is reduced, thereby reducing the side reactions between the negative electrode surface and the electrolyte during the charge and discharge process, and the coating on the surface of the negative electrode active material layer formed in the electrodeposition process acts as a protective layer.

[0137] Therefore, when the negative electrode is manufactured by the same method as in this embodiment, even if the electrodeposition process is performed under high current conditions, the performance of the negative electrode active material layer formed will not deteriorate, and the negative electrode active material layer can be formed quickly. Thus, the commercialization and production competitiveness of the negative electrode formed with the negative electrode active material layer containing the lithium metal layer can be ensured.

[0138] The present invention can be implemented in various different ways and is not limited to the above-mentioned embodiments. It will be appreciated by those skilled in the art that the present invention can be implemented in other specific ways without changing the technical concept or essential features of the present invention. Therefore, the above-mentioned embodiments are exemplary in all aspects and are not restrictive.

Claims

1. A lithium secondary battery negative electrode, comprising: a current collector; and a negative electrode active material layer, the negative electrode active material layer being located on at least one side of the current collector and comprising a lithium metal layer, The negative electrode active material layer including a lithium metal layer includes: a coating layer disposed on the current collector and comprising metal seeds; and a lithium metal layer, the lithium metal layer being located on the coating, The thickness of the coating layer is 100 nm to 500 nm.

2. The negative electrode of the lithium secondary battery according to claim 1, wherein The metal seed crystal is one or more selected from the group consisting of magnesium, silver, zinc, platinum, tin, silicon, aluminum, sodium, potassium, gold, bismuth, indium and germanium.

3. The negative electrode of the lithium secondary battery according to claim 1, wherein: The thickness of the negative electrode active material layer is 1 μm to 100 μm.

4. The negative electrode of the lithium secondary battery according to claim 1, wherein: The negative electrode active material layer further comprises: A coating film is located on the surface of the negative electrode active material layer, The coating film includes one or more substances selected from the group consisting of Li-NCHO-based ionic compounds, Li-PCHO-based ionic compounds and LiF.

5. A lithium secondary battery negative electrode, comprising: a current collector; and a negative electrode active material layer, the negative electrode active material layer being located on at least one side of the current collector and comprising a lithium metal layer, The negative electrode active material layer containing a lithium metal layer is a lithium metal layer containing metal seed crystals inside. The metal seed crystal is magnesium.

6. The negative electrode of the lithium secondary battery according to claim 5, wherein: The thickness of the negative electrode active material layer is 1 μm to 100 μm.

7. The negative electrode of the lithium secondary battery according to claim 5, wherein: The metal seed crystals included in the lithium metal layer are metal seed crystals that alloy with lithium in the lithium metal layer.

8. The negative electrode of the lithium secondary battery according to claim 5, wherein: The negative electrode active material layer further comprises: A coating film is located on the surface of the negative electrode active material layer, The coating includes one or more substances selected from the group consisting of Li-NCH-O based ionic compounds, Li-PCH-O based ionic compounds and LiF.

9. A method for manufacturing a negative electrode of a lithium secondary battery, comprising the following steps: forming a coating on at least one side of a current collector using a coating composition containing metal seeds; Positioning the current collector formed with the coating layer in a plating solution, and then positioning a lithium source at a predetermined distance from the coating layer; and applying a current between the current collector and the lithium source to form a lithium metal layer, The metal seed crystal is one or more selected from the group consisting of magnesium, silver, zinc, platinum, tin, silicon, aluminum, sodium, potassium, gold, bismuth, indium and germanium, In the step of forming the coating, The coating layer formed on at least one side of the current collector has a thickness of 100 nm to 500 nm.

10. The method for manufacturing a negative electrode for a lithium secondary battery according to claim 9, wherein: In the step of forming the lithium metal layer, the lithium metal layer is positioned on the coating layer formed on at least one side of the current collector to form a negative electrode active material layer having a plurality of layers.

11. The method for manufacturing a negative electrode for a lithium secondary battery according to claim 9, wherein: In the step of forming the lithium metal layer, the metal seed crystals contained in the coating layer formed on at least one side of the current collector are alloyed with lithium in the lithium metal layer and diffused into the inside to form a single negative electrode active material layer.

12. The method for manufacturing a negative electrode for a lithium secondary battery according to claim 9, wherein: In the step of applying current to form a lithium metal layer on at least one side of the current collector, the current density of the applied current is 0.1 mA / cm 2 Up to 100mA / cm 2 .

13. The method for manufacturing a negative electrode for a lithium secondary battery according to claim 12, wherein: In the step of applying current to form a lithium metal layer on at least one side of the current collector, the time for applying current is 0.05 hours to 50 hours.

14. The method for manufacturing a negative electrode for a lithium secondary battery according to claim 9, wherein: The step of forming a coating on at least one side of the current collector using a coating composition containing metal seeds adopts at least one method selected from the group consisting of sputtering, electroplating and electroless plating, electron beam deposition and thermal vapor deposition.

15. A lithium secondary battery comprising: negative electrode; A positive electrode; and Electrolytes, The negative electrode is the negative electrode for a lithium secondary battery according to any one of claims 1 to 8.

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