Negative active material including Si active metal grains and Cu—Al metal matrix surrounding Si active metal grains and rechargeable lithium battery including negative active material

A rechargeable lithium battery, comprising:

• a negative electrode including a negative active material, the negative active material including Si and/or Sn active metal grains in an amount ranging from 30 to 60 wt % and a metal matrix in amount ranging from 40 to 70 wt % including at least two metal elements and comprising a binary alloy including Cu and Al, the weight ratio of Cu:Al being 84:16 to 91:9, the metal matrix being configured to surround the active metal gains, the Cu reacts with the Al to prevent the Cu from reacting with the Si and producing Cu3Si compound, and the metal matrix forms β-phase Cu—Al alloy resulting in no Cu3Si compound;
• a positive electrode including a positive active material that reversibly intercalates and deintercalates lithium ions;
• and
• an electrolyte solution.