Herein, we present the synthesis and characterization of negative (a hard carbon/carbon black composite) and positive (K0.3MnO2) active materials for K-ion batteries as well as their combination in a non-aqueous K-ion cell. The hard carbon/carbon black composite can deliver up to 200 mAh g(-1) while the layered birnessite K0.3MnO2 delivers up to 136 mAh g(-1). The K-ion cell exhibits an interesting and encouraging cycling performance for 100 cycles. These exciting new insights demonstrate the potential of K-ion batteries, which are worth to be further investigated in greater detail. (C) The Author(s) 2016. Published by ECS. All rights reserved.