A 4 V Class Potassium Metal Battery with Extremely Low Overpotential

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Potassium (K) metal anodes suffer from low Coulombic efficiency and safety issues due to volume variations and high reactivity.
• Developing stable and high-performance K metal anodes is crucial for advancing K metal batteries.

Purpose of the Study:

• To engineer a stable three-dimensional K (3D-K) anode with improved electrochemical performance.
• To construct a high-performance K metal battery utilizing the novel anode.

Main Methods:

• Fabrication of a 3D-K anode by plating K onto hollow N-doped C polyhedrons/graphene (HNCP/G).
• Conformal coating of a Sn-based solid-electrolyte interphase (SEI) layer onto the 3D-K anode to form Sn@3D-K.
• Assembly and testing of symmetric Sn@3D-K cells and a full battery with a Prussian blue (PB)/graphene cathode.

Main Results:

• The Sn@3D-K anode demonstrated reduced interfacial resistance, enhanced K+ ion transport, suppressed parasitic reactions, and mitigated K dendrite formation.
• The HNCP/G host effectively accommodated volume changes, leading to low voltage hysteresis in symmetric cells (9 mV at 0.2 mA cm-2 after 500 h).
• The K1.56Mn[Fe(CN)6]1.08/G∥Sn@3D-K battery achieved a 4.02 V discharge plateau, ultralow 0.01 V overpotential, and 147.2 mAh g-1 specific capacity.

Conclusions:

• The Sn@3D-K anode significantly enhances the stability and electrochemical performance of potassium metal anodes.
• The developed 4V class K metal battery exhibits state-of-the-art performance, including extremely low overpotential and high specific capacity, surpassing previously reported PB-based K batteries.