A 3D structural NC/ZnO@carbon cloth matrix as a potassiophilic host for a dendrite-free potassium metal anode

Abstract

Metallic potassium batteries (PMBs), with natural abundance and relatively low operating potential, are considered one of the mighty alternatives to lithium-ion batteries. However, uncontrollable dendrite growth and large volume changes of the potassium metal anode have restrained their practical applications. Herein, we prepared a promising 3D structural potassiophilic NC/ZnO@carbon matrix (NC/ZnO@CC) as a host for a dendrite-free potassium metal anode. The COMSOL simulation demonstrates that the prepared ZnO nanorods are structurally favorable for uniform local current density, K⁺ concentration distribution and even ion flow. Additionally, experimental measurements and DFT calculations reveal that the potassiophilic NC/ZnO@CC provides stronger binding energy and lower migration barriers for K metal deposition, significantly enhancing the electrochemical kinetics and thermodynamics of K@NC/ZnO@CC. Meanwhile, the carbon matrix and the outer potassiophilic buffer NC layer of ZnO offer sufficient space for K deposition. Owing to these merits, the symmetric K@NC/ZnO@CC cell exhibits a low overpotential of 50 mV and a cycle life of more than 1200 h at a current density of 0.5 mA cm⁻² with an area capacity of 0.5 mA h cm⁻². Paired with a Prussian blue (KPB) cathode, the K@NC/ZnO@CC||PB full cell displays much improved rate performance and discharge capacity. This work provides an effective method toward achieving high energy density and dendrite-free potassium metal-based batteries.