Positive active material for rechargeable lithium battery and rechargeable lithium battery including same

A rechargeable lithium battery comprising:

• a negative electrode comprising a negative active material;
• a positive electrode comprising a positive active material comprising a composite material comprised of a microporous carbon-based material and a lithium composite compound formed by agglomerating the microporous carbon-based material and the lithium composite compound wherein the composite material comprises secondary particles comprising smaller primary particles of the microporous carbon-based material and the lithium composite compound agglomerated together, and the primary particles have an average particle size (D50) of 1 micrometer or less;
• and a carbon layer partially or entirely disposed partially or entirely on the surface of the secondary particles of the composite material;
• and
• a non-aqueous electrolyte, wherein
• the microporous carbon-based material comprises one of activated carbon, carbide derived carbon (CDC), expanded carbon, expanded graphite and a combination thereof, has an average particle size (D50) ranging from 100 nm or more and less than 1 μm, and has a specific surface area ranging from 50 m2/g to 3000 m2/g;
• the lithium composite compound comprising LiaA1-bXbD2 (0.90≦a≦1.8, 0≦b≦0.5);
• LiaA1-bXbO2-cDc (0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05);
• LiaE1-bXbO2-cDc (0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05);
• LiaE2-bXbO4-cDc (0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05);
• LiaNi1-b-cCobXcDα (0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.5, 0<α≦2);
• LiaNi1-b-cCobXcO2-αTα (0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05, 0<α<2);
• LiaNi1-b-cCobXcO2-αT2 (0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05, 0<α<2);
• LiaNi1-b-cMnbXcDα (0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05, 0<α≦2);
• LiaNi1-b-cMnbXcO2-αTα (0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05, 0<α<2);
• LiaNi1-b-cMnbXcO2-αT2 (0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05, 0<α<2);
• LiaNibEcGdO2 (0.90≦a≦1.8, 0≦b≦0.9, 0≦c≦0.5, 0.001≦d≦0.1);
• LiaNibCobMndGeO2 (0.90≦a≦1.8, 0≦b≦0.9, 0≦c≦0.5, 0≦d≦0.5, 0.001≦e≦0.1);
• LiaNiGbO2 (0.90≦a≦1.8, 0.001≦b≦0.1) LiaCoGbO2 (0.90≦a≦1.8, 0.001≦b≦0.1);
• LiaMnGbO2 (0.90≦a≦1.8, 0.001≦b≦0.1);
• LiaMn2GbO4 (0.90≦a≦1.8, 0.001≦b≦0.1);
• LiaMn1-gGgPO4 (0.90≦a≦1.8, 0<g≦0.5);
• wherein A in the above formulae being selected from the group consisting of Ni, Co, Mn, and a combination thereof;
• X in the above formulae being selected from the group consisting of Al, Ni, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, and a combination thereof;
• D in the above formulae being selected from the group consisting of O, F, S, P, and a combination thereof;
• E in the above formulae being selected from the group consisting of Co, Mn, and a combination thereof;
• T in the above formulae being selected from the group consisting of F, S, P, and a combination thereof;
• G in the above formulae being selected from the group consisting of Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, and a combination thereof;
• the lithium composite compound and the microporous carbon-based material being mixed in a ratio ranging from 51:49 wt % to 99:1 wt %;
• and
• the carbon layer is about 1 nm to about 500 nm thick.