Negative electrode active material and method of preparing the same

A negative electrode active material comprising a silicon-based alloy, wherein:

• the silicon-based alloy is represented by Si-M1-M2-C—B, wherein M1 and M2 are different from each other and are each independently selected from magnesium (Mg), aluminum (Al), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), gallium (Ga), germanium (Ge), manganese (Mn), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), silver (Ag), tin (Sn), tantalum (Ta), and tungsten (W),
• in the silicon-based alloy, an amount of Si is in a range of about 50 atom % to about 90 at %, an amount of M1 is in a range of about 10 at % to about 50 at %, and an amount of M2 is in a range of 0 at % to about 10 at %, based on a total number of Si, M1, and M2 atoms, and an amount of C is in a range of about 0.01 parts by weight to about 30 parts by weight, and an amount of B is in a range of 0 parts by weight to about 5 parts by weight, based on a total of 100 parts by weight of Si, M1, and M2,
• the silicon-based alloy includes:
• a matrix that includes at least one of a Si-M1 alloy phase and a Si-M2 alloy phase, and
• a Si single phase dispersed in the matrix, and
• C and B are each independently disposed on a surface of or inside the silicon-based alloy.