Herein, a novel operating life (OL) test method was evaluated with 200 mAh pouch-type lithium-ion batteries. By combining the calendar life (CL) test with intermediate pulse power cycling, more realistic life prediction was possible, which encompassed real operation of batteries accompanying with thermal acceleration. Larger capacity decrease and resistance increase of pouch cell were observed in the OL test, which was well explained using the SEI film growth model. After dissemble of pouch cell, capacity loss and resistance increase mostly occurred within anode, reflecting that SEI film growth on anode surface was highly attributable to cell degradation.​