KR20020094530A - Current collector coated with metal, electrodes comprising it, and lithium batteries comprising the electrodes - Google Patents

Abstract

PURPOSE: A current collector coated with a metal, an electrode employing the current collector and a lithium battery containing the electrode are provided to improve the conductivity and to allow the potential distribution on the surface of an electrode to be maintained uniformly, thereby enhancing the utilization rate of an electrode and the cycle characteristic and the charge/discharge characteristic of a battery. CONSTITUTION: The current collector is a foil, a punched foil, an expanded foil or a porous plate made of copper, nickel, aluminum or titanium, and whose both faces are coated with a metal with a thickness of several nm to several micrometers uniformly. Preferably the metal coating the current collector is selected from the group consisting of Ni, Cu, Ti, V, Cr, Mn, Fe, Co, Zn, Mo, W, Ag, Au, Ru, Pt, Ir, Al, Sn, Bi, Si, Sb and their alloys. The electrode comprises a lithium electrode made by coating the current collector with lithium; a carbon-coated carbon electrode; and a metal compound-coated metal compound electrode. The lithium battery comprises a cathode and an anode according to the electrode; a polypropylene or polyethylene separation membrane; and a polymer electrolyte or a solid electrolyte.

Description

A current collector coated with a metal, an electrode using the same, and a lithium battery including the same {{RRRRENT COLLECTOR COATED WITH METAL, ELECTRODES COMPRISING IT, AND LITHIUM BATTERIES COMPRISING THE ELECTRODES}

The present invention relates to a current collector coated with a metal, an electrode and a lithium battery using the same. More specifically, a metal containing silver, gold, platinum, or an alloy thereof on both surfaces of a current collector such as copper, nickel, aluminum, or titanium may be several nm to several μm by electroplating, electroless plating, physical vapor deposition, or chemical vapor deposition. The present invention relates to a current collector coated with a thickness, an electrode including the same, and a lithium battery including the electrode.

If the current collector for a lithium secondary battery is classified into its shape, there are a foil, a punched foil, an expanded foil, a porous plate, and the like. Copper is the negative electrode current collector. Nickel or titanium is used, and aluminum or titanium is used as the positive electrode current collector (see JO Besenhard, Handbook of Battery Materials, WILEY-VCH, Weinheim (1999)). I use it. However, in the case of a bel-core type lithium ion polymer battery, since the electrode active material and the current collector are not easily adhered to each other, carbon is coated on the expanded thin plate to increase the bonding force between them and reduce the interface resistance. It is different from the purpose.

Lithium batteries may be roughly classified into lithium primary batteries and lithium secondary batteries. Lithium primary batteries use lithium metal as a negative electrode, and are divided into Li-MnO ₂ , Li- (CF) _n, and Li-SOCl ₂ according to the type of positive electrode, and these are currently commercialized. (JO Besenhard, Handbook of Battery Materials, WILEY-VCH, Weinheim (1999). However, the lithium primary battery has a disadvantage in that the potential distribution is uneven due to local dissolution of the lithium electrode, thereby lowering the utilization rate of the electrode.

In the case of a lithium secondary battery, it is currently commercialized to use a carbon-based material as a negative electrode and to use LiCoO ₂ or LiMn ₂ O ₄ as a positive electrode, but much research has been conducted on lithium negative electrodes to increase energy density of a battery. (See D. Linden, Handbook of Batteries, McGRAW-HILL INC., New York (1995).) On the other hand, as the size of the battery increases, the conductivity of the current collector greatly affects the battery performance. Since the oxide film is naturally formed and acts as a resistance to high current flow, the limit of the current collector is revealed, and thus an improvement thereof is required.

Lithium electrodes have a very high capacity of 3860mAh / g in theory, but have low charging and discharging efficiency, and dendrite precipitates on the electrode surface during charging, which may cause an internal short circuit and cause an explosion. In addition, lithium currently reacts with the current collector of copper to form a lithium alloy, and this alloy has a reversibility and causes a decrease in the charge / discharge efficiency and utilization rate of lithium, which is an obstacle to the development of a secondary battery using lithium metal. .

Recently, in order to solve these problems, studies have been made to increase the charge and discharge efficiency by adding additives to the electrolyte, to change the form of lithium deposition, to study the mixing of metal fine particles such as nickel and copper, and to change the composition of the lithium alloy. (See the 35th Round Discussion Seminar Collection 103 (1994), the 36th Round Discussion Forum Abstract 147 (1995), and JO Besenhard, Handbook of Battery Materials, WILEY-VCH, Weinheim (1999).) This is not being presented.

SUMMARY OF THE INVENTION An object of the present invention is to provide a current collector on which both surfaces of a current collector, such as copper, nickel, aluminum, or titanium, are coated with a metal including silver, gold, platinum, or a heap gold thereof.

Still another object of the present invention is to maintain a constant distribution of potentials on the surface of the electrode, thereby increasing the utilization and cycle characteristics of the electrode and improving the high rate charge / discharge characteristics, including the current collector, the lithium electrode, the carbon electrode, and the metal compound electrode; It is to provide a lithium battery comprising such an electrode.

1 is a cross-sectional view of a current collector according to the present invention coated with a metal.

2 is a graph showing the electrode capacity and the life test results for the lithium secondary battery prepared in Examples 1 to 4, and Comparative Example 1.

3 is a graph showing high rate discharge characteristics of the lithium secondary batteries manufactured by Example 2 and Comparative Example 1. FIG.

4 is a graph showing discharge characteristics of Example 6 and Comparative Example 2 of a lithium primary battery including a lithium electrode manufactured from a current collector according to the present invention.

In the current collector according to the present invention, as shown in FIG. 1, a metal including silver, gold, platinum, titanium, or an alloy thereof is coated on both surfaces of a current collector such as copper, nickel, aluminum, or titanium with a thickness of several nm to several μm. It is desirable to be. The coating of the metal on the current collector with a thickness of several nm to several μm should be coated at such a thickness to exhibit electrical conductivity, which can serve as a current collector. If the coating is thicker, the volume and weight of the coated current collector itself are large. This is because the battery capacity is lowered and uneconomical because the amount of the positive electrode active material that can be filled in the inside of the battery having a limited size is relatively reduced. The metal to be coated is Ni, Cu, Ti, V, Cr, Mn, Fe, Co, Zn, Mo, W, Ag, Au, Ru, Pt, Ir, Al, Sn, Bi, Si, Sb, or alloys thereof It is selected from the group consisting of.

The current collector according to the present invention is prepared by coating a metal on both surfaces of a common current collector such as copper, nickel, aluminum, or titanium by an electroplating method, an electroless plating method, a physical vapor deposition method, or a chemical vapor deposition method. At this time, the physical vapor deposition method is preferably a method such as a thermal vapor deposition method, an electron beam deposition method, an ion beam deposition method, a sputtering method or a laser ablation. Features of the manufacturing method according to the present invention can be freely coated on both sides of the current collector of the metal or alloy of the desired type, can be coated with a pure metal composite without contamination by external factors, the composition of the metal by controlling the coating speed , Uniformity of coating, coating thickness and coating time can be adjusted.

The electrode according to the present invention has a form of a lithium electrode, a carbon electrode, and a metal compound electrode, each of which is coated with lithium, carbon or a metal compound on a metal-coated current collector. The coating method and coating thickness of the electrode active material are the same as those used in ordinary lithium primary batteries and lithium secondary batteries, except that the current collector of the present invention is used as the current collector. Metal compounds are also the same as those used in conventional lithium primary batteries and lithium secondary batteries. That is, examples of the metal compound coated on the metal-coated current collector include MnO ₂ , (CF) _n, LiCoO ₂ , LiNiO ₂ , LiNiCoO ₂ , LiMn ₂ O ₄ , V ₂ O _5, V ₆ O _13, Li _x CoPO ₄ , Li _x FePO ₄ , Li _x CaCoF _6, and the like.

The lithium battery can be manufactured using the electrode of the present invention. That is, a lithium primary battery is formed using MnO ₂ , (CF) _n or SOCl ₂ as a positive electrode, LiCoO ₂ , LiNiO ₂ , LiNiCoO ₂ , LiMn ₂ O ₄ , V ₂ O _5, V ₆ O _13, Li _x CoPO ₄ , Li _x FePO ₄ or Li _x CaCoF ₆ may be used as a positive electrode to manufacture a lithium secondary battery. In addition, the electrode according to the present invention is a lithium battery using a separator such as polypropylene (hereinafter referred to as PP) or polyethylene (hereinafter referred to as PE), a lithium polymer battery using a polymer electrolyte, and an all-solid type using a solid electrolyte. It can be used as an electrode of a lithium battery.

The following are examples and comparative examples of preparing a lithium electrode and a lithium battery according to the present invention and performing a performance test. Although the present invention will be described in more detail by this, these examples are merely illustrative of the present invention, the present invention is not limited thereto.

Example

Example 1

Gold is coated on both sides of the expanded copper sheet current collector by electroplating to a thickness of 100 nm to obtain a current collector coated with gold. 6 g of graphite (meso carbon micro bead = MCMB) and 0.4 g of polyvinylidene fluoride (hereinafter referred to as PVdF) are mixed with an appropriate amount of 1-methyl-2-pyrrolidone (hereinafter referred to as NMP) and acetone. Then, when a suitable viscosity is obtained, it is cast on a copper-clad current collector coated with gold, dried, and then rolled to obtain a graphite cathode. The LiCoO ₂ positive electrode was mixed with a composition of 5.7 g of LiCoO ₂ , 0.6 g of acetylene black (hereinafter referred to as AB) and 0.4 g of PVdF with an appropriate amount of NMP and acetone, and then cast on a thin sheet of aluminum when a suitable viscosity was obtained. After rolling, it is obtained. The graphite cathode, the PP separator, and the LiCoO ₂ anode were laminated to each other, and a lithium secondary battery was prepared by injecting 1M LiPF ₆ ethyl carbonate / ethyl methyl carbonate solution (hereinafter referred to as EC / EMC solution). The electrode capacity and cycle life based on the anode were investigated with C / 2.

Example 2

Both surfaces of the copper foil current collector are coated with gold at a thickness of 200 nm by electroplating to obtain a current collector coated with gold. On the current collector, lithium was coated on both sides by vacuum deposition to produce a lithium cathode. The LiCoO ₂ anode is obtained by mixing a composition of 5.7 g of LiCoO ₂ , 0.6 g of AB and 0.4 g of PVdF with an appropriate amount of NMP and acetone, then casting on a thin sheet of aluminum when the proper viscosity is obtained, drying and rolling. Lithium anode, PP separator and LiCoO ₂ positive electrode are laminated and manufactured by injecting 1M LiPF ₆ EC / EMC solution to manufacture a lithium secondary battery. Investigate.

Example 3

Gold is coated on both sides of the thin aluminum current collector to a thickness of 100 nm to obtain an aluminum current collector coated with gold. The LiCoO ₂ anode is obtained by mixing a composition of 5.7 g of LiCoO ₂ , 0.6 g of AB and 0.4 g of PVdF with an appropriate amount of NMP and acetone, then casting it on a gold-coated aluminum sheet when the proper viscosity is obtained, drying and rolling. . A carbon negative electrode was manufactured using a copper current collector in the same manner as in Example 1. Carbon anode, PP separator and LiCoO ₂ positive electrode were laminated, and lithium secondary battery was prepared by injecting 1M LiPF ₆ EC / EMC solution, and then the electrode capacity and cycle life based on the positive electrode were measured at charge / discharge rate C / 2. Investigate.

Example 4

Silver is coated on both surfaces of the copper foil current collector by a vacuum deposition method to a thickness of 200 nm to obtain a copper current collector coated with silver. Lithium anode was manufactured by coating lithium on both sides of the current collector by vacuum deposition on the both sides. The LiCoO ₂ anode is obtained by mixing a composition of 5.7 g of LiCoO ₂ , 0.6 g of AB and 0.4 g of PVdF with an appropriate amount of NMP and acetone, then casting on a thin sheet of aluminum when the proper viscosity is obtained, drying and rolling. Lithium anode, PP separator and LiCoO ₂ positive electrode are laminated and manufactured by injecting 1M LiPF ₆ EC / EMC solution to manufacture a lithium secondary battery. Investigate.

Example 5

Platinum is coated with a thickness of 200 nm on both surfaces of the copper foil current collector by sputtering to obtain a copper current collector coated with platinum. On the current collector, lithium was coated on both sides by vacuum deposition to produce a lithium cathode. The LiCoO ₂ anode is obtained by mixing a composition of 5.7 g of LiCoO ₂ , 0.6 g of AB and 0.4 g of PVdF with an appropriate amount of NMP and acetone, then casting on a thin sheet of aluminum when the proper viscosity is obtained, drying and rolling. Lithium anode, PP separator and LiCoO ₂ positive electrode are laminated and manufactured by injecting 1M LiPF ₆ EC / EMC solution to manufacture a lithium secondary battery. Investigate.

Example 6

Both surfaces of the copper foil current collector are coated with gold at a thickness of 200 nm by electroplating to obtain a copper current collector coated with gold. Lithium anode was manufactured by coating lithium on both sides of the current collector by vacuum deposition on the both sides. The MnO ₂ anode is obtained by mixing a composition of 5.7 g of MnO ₂ , 0.6 g of AB and 0.4 g of PVdF with an appropriate amount of NMP and acetone, then casting on a thin sheet of aluminum when the proper viscosity is obtained, drying and rolling. A lithium cathode, a PP separator, and an MnO ₂ anode were stacked to form a lithium primary battery by injecting a 1M LiPF ₆ EC / EMC solution, and then discharge characteristics were investigated at a discharge rate of C / 10.

Comparative example

Comparative Example 1

A lithium negative electrode having a thickness of 100 μm was pressed to an 80 μm thickness on an expanded copper thin plate to prepare a lithium negative electrode. The LiCoO ₂ anode is obtained by mixing a composition of 5.7 g of LiCoO ₂ , 0.6 g of AB and 0.4 g of PVdF with an appropriate amount of NMP and acetone, then casting on a thin sheet of aluminum when the proper viscosity is obtained, drying and rolling. The lithium cathode, the PP separator and the LiCoO ₂ positive electrode were laminated, and a lithium secondary battery was prepared by injecting 1M LiPF ₆ EC / EMC solution. The lifetime was investigated.

Comparative Example 2

A 50 μm thick lithium platen is pressed onto a copper foil to 40 μm to prepare a lithium electrode. The MnO ₂ anode is obtained by mixing a composition of 5.7 g of MnO ₂ , 0.6 g of AB and 0.4 g of PVdF with an appropriate amount of NMP and acetone, then casting on a thin sheet of aluminum when the proper viscosity is obtained, drying and rolling. A lithium cathode, a PP separator, and an MnO ₂ anode were stacked to form a lithium primary battery by injecting a 1M LiPF ₆ EC / EMC solution, and then discharge characteristics were investigated at a discharge rate of C / 10.

The electrode capacity and the cycle characteristics of the lithium secondary batteries manufactured according to Examples 1 to 5 and Comparative Example 1 were examined and shown in FIG. 2. While the batteries according to the present invention have excellent electrode capacity and cycle life characteristics, it can be seen that the battery prepared in Comparative Example 1 has poor electrode capacity and cycle life characteristics. 3 shows the high rate discharge characteristics (1C) of the lithium secondary batteries according to Example 2 and Comparative Example 1, showing that the high rate discharge characteristics of the battery according to the present invention is more excellent.

Figure 4 shows the results of the discharge characteristics of the lithium primary battery prepared in Example 6 and Comparative Example 2, showing that the discharge characteristics of the battery according to the present invention is more excellent.

According to the present invention, a current collector coated with a metal, an electrode using the same, and a lithium battery including the electrode are provided.

Since the electrode manufactured using the current collector according to the present invention having improved conductivity is superior to the conventional electrode, the utilization rate, cycle life characteristics, and high rate charge / discharge characteristics of the electrode, the lithium battery including the electrode includes various small electronic devices, It is expected to be applied in various industrial fields such as power supply of communication equipment and electric vehicle.

Claims (6)

A current collector in which metal is uniformly coated with a thickness of several nm to several μm on both sides of a current collector in the form of a thin plate, a perforated thin plate, an expanded thin plate or a porous thin plate made of copper, nickel, aluminum, or titanium. The method of claim 1, wherein the metal to be coated is Ni, Cu, Ti, V, Cr, Mn, Fe, Co, Zn, Mo, W, Ag, Au, Ru, Pt, Ir, Al, Sn, Bi, Si, A current collector selected from the group consisting of Sb and their alloys. An electrode comprising a lithium electrode coated with lithium, a carbon electrode coated with carbon, and a metal compound coated metal compound on the current collector according to claim 1. A lithium battery comprising a negative electrode and a positive electrode according to claim 3, a PP or PE separator, and a polymer electrolyte or a solid electrolyte. The lithium primary battery of claim 3, wherein the lithium electrode according to claim ₃ is an anode, and an active material selected from the group consisting of MnO ₂ , (CF) _n, and SOCl ₂ is an anode. A lithium secondary battery comprising a lithium electrode or a carbon electrode according to claim 3 as a negative electrode, and a metal compound electrode according to claim 3 as a positive electrode.