Negative active material for rechargeable lithium battery, method of preparing the same, and rechargeable lithium battery including the same

Abstract

The present invention provides a negative active material for a rechargeable lithium battery, including an inner layer including a material being capable of doping and dedoping lithium, a carbon layer outside the inner layer, and an outer layer disposed on the carbon layer and including a material being capable of doping and dedoping lithium. The materials being capable of doping and dedoping lithium included in the inner layer and in the outer layer may be the same or different from each other.

1 . A negative active material for a rechargeable lithium battery, comprising:
 an inner layer comprising a material capable of doping and dedoping lithium;   a carbon layer disposed outside the inner layer; and   an outer layer disposed on the carbon layer and comprising a material capable of doping and dedoping lithium,   wherein the materials capable of doping and dedoping lithium in the inner layer and in the outer layer are the same or different from each other.   
     
     
         2 . The negative active material of  claim 1 , which has a tube or bar shape. 
     
     
         3 . The negative active material of  claim 2 , wherein the tube-shaped negative active material further has a hollow part inside the inner layer. 
     
     
         4 . The negative active material of  claim 1 , wherein the material being capable of doping and dedoping lithium in the inner layer comprises one selected from the group consisting of silicon (Si), a Si—Y1 alloy, tin (Sn), a Sn—Y2 alloy, antimony (Sb), germanium (Ge), lead (Pb), and a combination thereof, wherein Y1 and Y2 are the same or different and are selected from the group consisting of an alkali metal, an alkaline-earth metal, a group 13 element, a group 14 element, a transition element, a rare earth element, and a combination thereof, provided that Y1 is not silicon (Si) and Y2 is not tin (Sn). 
     
     
         5 . The negative active material of  claim 4 , wherein the Y1 and Y2 comprise one selected from the group consisting of magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), scandium (Sc), yttrium (Y), titanium (Ti), zirconium (Zr), hafnium (Hf), rutherfordium (Rf), vanadium (V), niobium (Nb), tantalum (Ta), dubnium (Db), chromium (Cr), molybdenum (Mo), tungsten (W), seaborgium (Sg), technetium (Tc), rhenium (Re), bohrium (Bh), iron (Fe), lead (Pb), ruthenium (Ru), osmium (Os), hassium (Hs), rhodium (Rh), iridium (Ir), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), cadmium (Cd), boron (B), aluminum (Al), gallium (Ga), silicon (Si), tin (Sn), indium (In), germanium (Ge), phosphorus (P), arsenic (As), antimony (Sb), bismuth (Bi), sulfur (S), selenium (Se), tellurium (Te), polonium (Po), and a combination thereof. 
     
     
         6 . The negative active material of  claim 1 , wherein the material being capable of doping and dedoping lithium in the outer layer comprises silicon (Si), SiOx (0<x<2), a Si—Y3 alloy, tin (Sn), SnO2, a Sn—Y4 alloy, antimony (Sb), germanium (Ge), lead (Pb), and a combination thereof, wherein Y3 and Y4 are the same or different and are selected from the group consisting of an alkali metal, an alkaline-earth metal, a group 13 element, a group 14 element, a transition element, a rare earth element, and a combination thereof, provided that Y3 is not silicon (Si) and Y4 is not tin (Sn). 
     
     
         7 . The negative active material of  claim 6 , wherein Y3 and Y4 comprise one selected from the group consisting of magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), scandium (Sc), yttrium (Y), titanium (Ti), zirconium (Zr), hafnium (Hf), rutherfordium (Rf), vanadium (V), niobium (Nb), tantalum (Ta), dubnium (Db), chromium (Cr), molybdenum (Mo), tungsten (W), seaborgium (Sg), technetium (Tc), rhenium (Re), bohrium (Bh), iron (Fe), lead (Pb), ruthenium (Ru), osmium (Os), hassium (Hs), rhodium (Rh), iridium (Ir), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), cadmium (Cd), boron (B), aluminum (Al), gallium (Ga), silicon (Si), tin (Sn), indium (In), germanium (Ge), phosphorus (P), arsenic (As), antimony (Sb), bismuth (Bi), sulfur (S), selenium (Se), tellurium (Te), polonium (Po), and a combination thereof. 
     
     
         8 . The negative active material of  claim 1 , wherein the carbon layer outside the inner layer is amorphous. 
     
     
         9 . The negative active material of  claim 1 , wherein the materials being capable of doping and dedoping lithium in the inner and outer layers have a weight ratio ranging from about 10:90 to about 50:50. 
     
     
         10 . The negative active material of  claim 1 , which has a specific surface area ranging from about 2 to about 70 m 2 /g. 
     
     
         11 . The negative active material of  claim 1 , which has a length ranging from about 5 μm to about 200 μm and a diameter ranging from about 200 nm to about 300 nm. 
     
     
         12 . The negative active material of  claim 1 , wherein the outer layer has a thickness ranging from about 10 nm to about 50 nm. 
     
     
         13 . The negative active material of  claim 1 , which further comprises a carbon layer inside the inner layer. 
     
     
         14 . The negative active material of  claim 13 , wherein the carbon comprised in the carbon layer outside the inner layer and the carbon comprised in the carbon layer inside the inner layer are amorphous. 
     
     
         15 . A method of preparing a negative active material for a rechargeable lithium battery, comprising:
 preparing a tube-shaped template with a hollow part;   forming an outer layer comprising a material being capable of doping and dedoping lithium inside the template;   forming an inner precursor layer comprising a material being capable of doping and dedoping lithium which is modified with an organic functional group inside the outer layer;   annealing the template; and   removing the template.   
     
     
         16 . The method of  claim 15 , wherein the organic functional group is represented as CnHm, and wherein the n and m are integers of 1 or more. 
     
     
         17 . The method of  claim 16 , wherein the organic functional group is selected from the group consisting of a C1 to C30 aliphatic group, a C3 to C30 alicyclic group, a C6 to C30 aromatic group, and a combination thereof. 
     
     
         18 . The method of  claim 15 , wherein the annealing is performed at a temperature ranging from about 700° C. to about 1100° C. 
     
     
         19 . The method of  claim 15 , wherein the template is removed using a basic or acidic material. 
     
     
         20 . The method of  claim 19 , wherein the basic material or the acidic material has a about 1 M to about 6 M concentration. 
     
     
         21 . A rechargeable lithium battery comprising:
 a negative electrode comprising a negative active material;   a positive active material comprising a positive active material; and   an electrolyte,   wherein the negative active material is from  claim 1 .