Patent ID: 8574764

Claim:
A negative active material for a rechargeable lithium battery, comprising: Si active particles in an amount of 30 to 70 wt % based on the weight of the negative active material; and a metal matrix being a three component metal matrix surrounding the Si active particles without chemically reacting with the Si active particles, the metal matrix comprising Cu, Al, and an additive metal, the Si active particles and the metal matrix being present in an alloy represented by Formula 1: x Si- y ( a Cu- b Al)- z X (1), Formula 1 having limitations including: x ranges from 30 to 70 wt %; y ranges from 30 to less than 70 w-t %; z is more than 0 wt % and 30 wt % or less; x+y+z is 100 wt %, and y+z is 30 to 70 wt %; when a+b is 100 wt %, a weight ratio of a and b ranges from 70:30 to 95:5; and X is the additive metal forming a solid-solution alloy with Cu and Al and is Sn.