Li-ion cells offer excellent energy storage and conversion characteristics, but also suffer from performance and safety problems related to overheating due to insufficient heat removal during operation. Traditional thermal management approaches cool the cell at its outer surface, whereas it is more critical to cool the core of the cell where heat accumulation occurs. This paper investigates thermal performance of a 26650 Li-ion cell with a heat pipe inserted into the core. Heat pipe integrated cells are assembled starting from unfilled, unsealed cells. Thermal benefit of heat pipe insertion is characterized at a number of discharge rates. Advantages of heat pipe cooling compared to traditional surface-based cooling approach are quantified. It is shown that active cooling of the protruding tip of the heat pipe results in maximum thermal benefit, which is shown to reduce the core temperature to as low as, or even lower than the surface temperature. The heat pipe is shown to reduce temperature rise in case of anomalous increase in heat generation. While heat pipe insertion involves significant manufacturing challenges to ensure long-term reliability, the thermal benefits in doing so may potentially outweigh these challenges, and offer an effective thermal management approach for future Li-ion cell designs. (C) 2017 The Electrochemical Society. All rights reserved.