Potassium Dual-Ion Hybrid Batteries with Ultrahigh Rate Performance and Excellent Cycling Stability.

Potassium-ion batteries (KIBs) are regarded as a potential alternative battery technology to conventional lithium-ion batteries owing to their low potential, natural abundance, and the low cost of potassium. However, sluggish reaction kinetic of the much larger K ions leads to low rate capability and poor cycling performance of KIBs, restricting KIB's practical applications. Herein, we propose a novel full battery called a potassium dual-ion hybrid battery (KDHB) by employing an absorption-type hierarchical porous carbon as the anode material and an anion intercalation-type expanded graphite (EG) as the cathode material. Owing to the hybrid mechanism of the battery and capacitive reaction, the KDHB exhibits superior rate performance with a high capacity of 82 mA h g even at a high current density of 3 A g with negligible capacity decay. Moreover, the KDHB exhibits excellent cycling performance with 74.2% capacity retention after 2000 cycles at 1 A g, which is so far the best performance of the reported KDIBs.