Lithium secondary battery with high energy density

Abstract

The present invention relates to electrodes for a lithium secondary battery with a high energy density and a secondary battery with a high energy density using the same. A negative electrode includes a material which can be alloyed with lithium alloy. A positive electrode is made of a transition metal oxide which can reversibly intercalate or deintercalate lithium. Here, the entire reversible lithium storage capacity of the positive electrode is greater than the capacity of lithium dischargeable from the positive electrode. Further, the present invention relates to electrodes for a lithium secondary battery in which metal lithium is coated on a negative electrode, a positive electrode, or both, a method of manufacturing the electrodes, and a lithium secondary battery including the electrodes. The lithium secondary battery of the present invention is excellent in safety because metal lithium does not remain after being activated and excellent in a capacity per unit weight.

1 . A lithium secondary battery, comprising:
 a negative electrode made of a material which can be alloyed with lithium;   a positive electrode made of a transition metal oxide capable of reversibly intercalating and deintercalating lithium and configured to have an entire reversible lithium storage capacity greater than a lithium capacity dischargeable from the positive electrode; and   a lithium layer formed on a surface of the negative electrode or the positive electrode or both.   
     
     
         2 . The lithium secondary battery of  claim 1 , wherein the lithium layer satisfies an Equation below.
     S<L≦S+I      where S=a lithium storage capacity of the positive electrode−a capacity of lithium initially included in the positive electrode, L is an amount of lithium within the lithium layer, and I is an initial irreversible consumption capacity in the negative electrode.   
     
     
         3 . The lithium secondary battery of  claim 1 , wherein after the lithium secondary battery is initially activated and charged, lithium of a metal form does not remain in the electrode surface. 
     
     
         4 . The lithium secondary battery of  claim 1 , wherein the material which can be alloyed with lithium has a capacity per unit weight of 700 mAh/g to 4300 mAh/g. 
     
     
         5 . The lithium secondary battery of  claim 1 , wherein the lithium layer is formed using a method of compressing a metal foil on the electrode surface, a method of depositing metal lithium on the electrode surface, or a method of dispersing and coating particles, including an excessive amount of metal lithium, together with a specific binder polymer on the electrode surface. 
     
     
         6 . The lithium secondary battery of  claim 1 , wherein the lithium layer has weight per unit area is 0.3 mg/cm 2  to 0.8 mg/cm 2 . 
     
     
         7 . The lithium secondary battery of  claim 1 , wherein the material which can be alloyed with lithium includes one or more selected from a group comprising Si, Sn, and Al; an alloy in which the atomic fraction of the element(s) is 50% or more; or an oxide of them. 
     
     
         8 . The lithium secondary battery of  claim 1 , wherein an initial irreversible capacity of the negative electrode is 40% or less of a reversible capacity. 
     
     
         9 . The lithium secondary battery of  claim 1 , wherein the transition metal oxide includes one or more selected from a group comprising MnO 2 , MoO 3 , VO 2 , V 2 O 5 , V 6 O 13 , Cr 3 O 8 , and CrO 2 . 
     
     
         10 . A negative electrode for a lithium secondary battery, comprising:
 a current collection plate;   an active material layer for the negative electrode, included in one or both sides of the current collection plate and made of a material which can be alloyed with lithium having a capacity per unit weight of 700 mAh/g to 4300 mAh/g; and   a lithium layer formed on the active material layer.   
     
     
         11 . The negative electrode of  claim 10 , wherein the lithium layer satisfies an Equation below.
     S<L≦S+I      where S=a lithium storage capacity of a positive electrode−a capacity of lithium initially included in the positive electrode, L is an amount of lithium within the lithium layer, and I is an initial irreversible consumption capacity in the negative electrode.   
     
     
         12 . A positive electrode for a lithium secondary battery, comprising:
 a current collection plate;   an active material layer for the positive electrode, included in one or both sides of the current collection plate and made of a transition metal oxide, not including lithium and enabling lithium intercalation and deintercalation, a transition metal oxide including lithium, or a mixture of them; and   a lithium layer formed on the active material layer.   
     
     
         13 . The positive electrode of  claim 12 , wherein the lithium layer satisfies an Equation below.
     S<L≦S+I      where S=a lithium storage capacity of the positive electrode−a capacity of lithium initially included in the positive electrode, L is an amount of lithium within the lithium layer, and I is an initial irreversible consumption capacity in a negative electrode.   
     
     
         14 . A method of manufacturing electrodes for a lithium secondary battery, the method comprising the step of:
 forming a lithium layer using a method of coating an electrode active material on an electrode current collection plate and compressing a metal foil on the electrode active material, a method of depositing metal lithium, or a method of dispersing and coating particles, including an excessive amount of metal lithium, together with a binder polymer.