A novel current collector design for anode-free K metal is achieved by integrating Bi microparticles into a CNT network via a simple slurry-casting method. The strong affinity between Bi and K as well as the ample internal space promotes uniform K nucleation and deposition on the Bi@CNT current collector, rendering ultrahigh CE and remarkable capacity retention of K@Bi@CNT||PTCDA full cells.

Abstract

Anode-free potassium metal batteries hold significant promise for cost-effective, large-scale energy storage due to the natural abundance of potassium and its high energy density. However, practical applications have been hindered by challenges such as dendrite formation and volume expansion during cycling. To address these issues, we present a scalable strategy that incorporates bismuth microparticles into a CNT network, forming a 3D current collector (Bi@CNT). This design facilitates uniform K deposition and mitigates volume changes, leveraging the strong affinity between Bi and K as well as the ample internal space provided by the porous CNT network. The Bi@CNT current collector demonstrates exceptional reversibility and cycling stability, maintaining consistent performance for over 4100 hours under periodic current fluctuations (0.1–2.0 mA cm⁻²) with an areal capacity of 0.5 mAh cm⁻² in no-reservoir asymmetric cells. When paired with a PTCDA cathode, the K@Bi@CNT||PTCDA full cell achieves an ultrahigh CE of ~99.9 % and remarkable capacity retention of ~92 % after 500 cycles at 200 mA g⁻¹. These results underscore the potential of Bi@CNT current collectors in advancing the development of anode-free K metal batteries for practical applications.