Fast and homogeneous ion regulation toward a 4 V, high-rate and dendrite-free potassium metal battery

Abstract

The uneven distribution and slow diffusion kinetics of potassium ions (K+) result in the formation and growth of K dendrites as well as poor rate capabilities, restricting the development of K metal anodes (KMAs). Paired with a Mn-based Prussian blue (PB) cathode, the KMA-based full battery exhibits a low average discharging voltage of ≈3.6 V and a high overpotential. Herein, a N-doped graphene nanomesh (NGM) acts as a conductive and potassiophilic host to solve this issue. First, the NGM enables K+ ions to rapidly transport its nanopores and edges to reach the whole electrode, offering unblocked transport channels for K+ ions and thus acquiring an enhanced rate capability. Second, the N atoms and defects within NGM reduce the nuclear energy barrier of K+ ions and induce their homogeneous deposition, avoiding the formation of K dendrites. Third, the nano-/micro-pores within NGM can accommodate the volume exchange of KMA during cycles, improving its cycling stability. Benefiting from these merits, the symmetric K@NGM cell delivers an ultra-low overpotential of 12.4 mV after 1700 h. Matched with a K1.7Mn[Fe(CN)6]0.9/graphene cathode, a 4 V and dendrite-free KMnHCF/G‖K@NGM full cell is designed, which exhibits excellent cycling stabilities and rate capabilities.