A battery pack includes: a first battery cell group including at least one high capacity battery cell; and a second battery cell group including at least one high output battery cell and being coupled in parallel to the first battery cell group, wherein the high output battery cell is configured to output a greater current than the high capacity battery cell, the high capacity battery cell is configured to store a greater amount of electric energy compared to the high output battery cell, and the battery pack is configured to operate in one of operational modes including: a high capacity mode for outputting electric energy stored in the first battery cell group; a high output mode for outputting electric energy stored in the second battery cell group; and a mutual charge mode for charging the first battery cell group or the second battery cell group.