Engineering Hollow Carbon Architecture for High-Performance K-Ion Battery Anode.

K-ion batteries (KIBs) are now drawing increasing research interest as an inexpensive alternative to Li-ion batteries (LIBs). However, due to the large size of K+, stable electrode materials capable of sustaining the repeated K+ intercalation/deintercalation cycles are extremely deficient especially if a satisfactory reversible capacity is expected. Herein, we demonstrated that the structural engineering of carbon into a hollow interconnected architecture, a shape similar to the neuron-cell network, promised high conceptual and technological potential for a high-performance KIB anode. Using melamine-formaldehyde resin as the starting material, we identify an interesting glass blowing effect of this polymeric precursor during its carbonization, which features a skeleton-softening process followed by its spontaneous hollowing. When used as a KIB anode, the carbon scaffold with interconnected hollow channels can ensure a resilient structure for a stable potassiation/depotassiation process and deliver an extraordinary capacity (340 mAh g-1 at 0.1 C) together with a superior cycling stability (no obvious fading over 150 cycles at 0.5 C).