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

A negative active material for a rechargeable lithium battery, the negative active material comprising:

• a secondary particle in which a plurality of primary particles are agglomerated, the plurality of primary particles comprising natural graphite, and the secondary particle comprising pores;
• and
• an amorphous carbon filled in the pores,
• wherein an area of the amorphous carbon is 10% to 30% based on a total area of 100% of the negative active material, in a cross-section through a center diameter of the secondary particle of the negative active material, and
• wherein the natural graphite is flake graphite.