Ternary chalcogenide anodes for high-performance potassium-ion batteries and hybrid capacitors via composition-mediated bond softening and intermediate phase

Despite the high potassium-ion storage of chalcogenide anodes relative to intercalation-based graphite, inhibition of their large volume change during the potassiation/depotassiation process, and stabilization of reversible electrochemical reactions to ensure efficient electron/ion transfer remain challenging. Here we report composition-tunable ternary chalcogenides that achieve highly reversible potassium-ion storage through synergistic interactions between elements. A series of Bi2−xSbxSe3 ternary chalcogenide (x = 0, 0.25, 1, 1.75, 2) solid solutions with a full composition range are designed using a facile high energy mechanical milling method. Sb2Se3 substituted by Bi gives rise to a chemical bond softening effect that accompanies structural transition and maintains excellent structural stability. Meanwhile, the intermediate quaternary-phase K3(Bi,Sb)Se3 enables a highly reversible 12-electron transfer conversion/alloying reaction during the potassiation/depotassiation process. Various electrochemical analyses show that Bi2−xSbxSe3 inherits the advantages of binary Sb2Se3 (high capacity) and Bi2Se3 (stability) while balancing their respective disadvantages, confirming the synergistic effect of ternary chalcogenide systems. By engineering Bi2−xSbxSe3 implemented into potassium-ion based full cells, we demonstrate a high energy/power density of 76.9 W h kg−1/1964.2 W kg−1 for batteries and 54.3 W h kg−1/3685.7 W kg−1 for hybrid capacitors. This work illustrates how to exploit the underlying multilateral science and the relevant electrochemistry of ternary chalcogenides to achieve excellent electrochemical performance, suggesting a new avenue of anode design for potassium-ion storage.