Electrode for rechargeable lithium battery and rechargeable lithium battery
An electrode having a current collector and, formed thereon, a thin film comprising an active material, characterized in that a thin alloy film (such as Sn—Co) comprising a metal which can form an alloy with lithium (such as Sn) and a metal which can not form an alloy with lithium (such as Co) is formed on a current collector such as a copper foil. It is preferred that the above metal which can form an alloy with lithium and the above metal which can not form an alloy with lithium can not form an intermetallic compound with each other.
1. A rechargeable lithium battery comprising a positive electrode, a nonaqueous electrolyte and a negative electrode, wherein said negative electrode has a current collector and a thin alloy film provided on the current collector and composed of a metal which alloys with lithium and a metal which does not alloy with lithium, said electrode being characterized in that said current collector has a surface roughness Ra of 0.1 μm–2 μm, said thin alloy film contains 0.1–50% of the metal which does not alloy with lithium based on a molar ratio (atomic ratio), the thin alloy film has a surface with irregularities corresponding to those defined on a surface of the current collector, and the thin alloy film is separated into islands by gaps formed, on the first or subsequent cycle of charge and discharge, along lines extending in a thickness direction of the thin alloy film between valleys of the irregularities on the thin alloy film surface and on the current collector surface.
2. The rechargeable lithium battery as recited in claim 1 , characterized in that the metal which alloys with lithium is a metal that forms an intermetallic compound with the metal which does not alloy with lithium.
3. The rechargeable lithium battery as recited in claim 1 , characterized in that said thin alloy film is deposited on the current collector by a plating process.
4. The rechargeable lithium battery as recited in claim 1 , characterized in that said current collector has a surface roughness Ra of 0.1–1 μm.
5. The rechargeable lithium battery as recited in claim 1 , characterized in that said current collector is composed of copper.
6. The rechargeable lithium battery as recited in claim 1 , characterized in that said current collector comprises an electrolytic copper foil.
7. The rechargeable lithium battery as recited in claim 1 , characterized in that the metal which alloys with lithium is Sn and the metal which does not alloy with lithium is a metal that forms an intermetallic compound with Sn.
8. The rechargeable lithium battery as recited in claim 7 , characterized in that the metal which alloys with lithium is Sn and the metal which does not alloy with lithium contains at least one metal selected from Fe, Co and Ni.
9. The rechargeable lithium battery as recited in claim 1 , characterized in that the metal which alloys with lithium is Sn, and at least Co is contained as the metal which does not alloy with lithium.
10. The rechargeable lithium battery as recited in claim 9 , characterized in that the metal which alloys with lithium is Sn, the metal which does not alloy with lithium is Co, and said thin alloy film comprises an Sn—Co alloy.
11. The rechargeable lithium battery as recited in claim 9 , characterized in that the metal which alloys with lithium is Sn, the metal which does not alloy with lithium contains Ni and Co, and said thin alloy film comprises an Sn—Ni—Co alloy.
12. The rechargeable lithium battery as recited in claim 1 , characterized in that a mixed layer of components of said current collector and thin alloy film is formed at an interface therebetween.