Rigid-Flexible Coupling Carbon Skeleton and Potassium-Carbonate-Dominated Solid Electrolyte Interface Achieving Superior Potassium-Ion Storage

Potassium-ion energy-storage devices are highly attractive in the large-scale energy storage field, but the intercalation of large K ions greatly worsens the stability of electrode structures and solid electrolyte interphase (SEI) films, causing slow reaction dynamics and poor durability. In this Article, inspired by bubble wraps in our life, a bubble-wrap-like carbon sheet (BPCS) with a rigid-flexible coupling porous architecture is fabricated on the microscale, exhibiting strong structural stability and good accommodation for volume expansion. In the meantime, a K2CO3·1.5H2O-dominated SEI is created by an interfacial transfer behavior of carbonate groups. These K2CO3·1.5H2O nanograins not only enhance the stability of the SEI by constructing a stable scaffold but also create more diffusion routes for K ions. On the basis of the above, using the BPCS as the anode of potassium-ion batteries delivers reversible capacities of 463 mAh g–1at 50 mA g–1and 195 mAh g–1at 10 A g–1with a long cycling life. The assembled BPCS//NPC potassium-ion hybrid capacitor exhibits a high energy density of 167 Wh kg–1and a superior cycling capability with 80.8% capacity retention over 10 000 cycles with nearly 100% Coulombic efficiency. Even at the higher current density of 10 A g–1, the device could deliver an energy density of 92.9 Wh kg–1over 5000 cycles at a power density of 9200 W kg–1with only 0.002% fading per cycle, which can rival lithium-ion hybrid supercapacitors.