Flexible N doped carbon/bubble-like MoS core/sheath framework: Buffering volume expansion for potassium ion batteries.

Suitable anode materials for potassium ion batteries (KIBs) with high capacity, good reversibility and stable cycling performances are still in large demand. Here, flexible N doped carbon/bubble-like MoS core/sheath framework (MoS/NCS) is prepared as an anode material for potassium ion batteries. The N doped carbon sponge (NCS) skeleton with good conductivity and high surface area guarantees superior rate capability and high stability of MoS/NCS anode. The chemical bonds (CMo) firmly bridge MoS and NCS together, which further ensures MoS/NCS stable cycling performance. More importantly, volume expansion is greatly buffered during cycling by this unique structure: the voids between bubble-like MoS sheath and NCS core can effectively buffer volume expansion generated during potassium intercalation/deintercalation; the enlarged interlayer spacing contribute more space to buffer volume change; the ultrathin nanosheets can shorten the charge diffusion distance and buffer volume change. As a consequence, MoS/NCS delivers a capacity of 374 mAh g over 200 cycles at 50 mA g. Even at 1000 mA g, a capacity of 212 mAh g can still be obtained over 1000 cycles. We believe this MoS/NCS structure will highlight the potential of MoS in practical KIBs applications.