Conductive metal organic framework mediated Sb nanoparticles as high-capacity anodes for rechargeable potassium-ion batteries

Abstract

The natural abundance of K in the earth crust and ocean and its low redox potential make potassium-ion batteries (PIBs) a feasible substitute for lithium-ion batteries. However, PIB anodes are still limited by slow reaction kinetics due to a large K-ion radius. Herein, for the first time, Sb@Ni3(HHTP)2 (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) composites are utilised as high-capacity anodes for rechargeable PIBs. In the composites, Sb nanoparticles are homogenously enveloped by a conductive metal–organic-framework (MOF), namely, Ni3(HHTP)2. The empirical results demonstrate that the composites undergo a consecutive reversible phase transformation from Sb to KSb2, KSb, K5Sb4, and K3Sb at different potentials during the potassiation–depotassiation phenomenon. An optimised Sb@Ni3(HHTP)2–10 electrode delivers high reversible capacities of 590 and 431 mAh g−1 at specific currents of 100 and 1000 mA g−1 after 100 and 300 cycles, respectively. The full cell, which is composed of the Sb@Ni3(HHTP)2 anode and a potassium ferrous ferricyanide cathode, provides a reversible capacity of 514 mAh g−1 at a specific current of 500 mA g−1. The excellent capacity performances of the Sb@Ni3(HHTP)2 anode prove that it is among the best PIB anodes reported until now. The exceptional performance of Sb@Ni3(HHTP)2 is attributed to the efficient coating of Sb nanoparticles by the conductive Ni3(HHTP)2 MOF as well as the formation of a strong KF-rich solid electrolyte interphase layer on the Sb@Ni3(HHTP)2 electrode in a concentrated electrolyte of 3 M potassium bis(fluorosulfonyl)imide in ethylene carbonate/diethyl carbonate.