Hard carbon as a negative electrode material for potassium-ion batteries prepared with high yield through a polytetrafluoroethylene-based precursor

Abstract

A new additive (polytetrafluoroethylene, PTFE) to typical sugar precursors for hard carbon (HC) preparation via hydrothermal carbonization has been proposed and investigated. The HC samples obtained from sugars (D-glucose and pectin) with and without PTFE were characterized with X-ray powder diffraction, Raman spectroscopy, scanning and transmission electron microscopy, energy-dispersive X-ray and electron energy loss spectroscopy, specific surface area measurements. Adding PTFE to sugars significantly improves the HC yield from <10% to 28% per total precursor mass as PTFE pyrohydrolysis generates small hollow HC nanospheres of 200-250 nm in diameter which then act as seeds for carbonization of sugars. Employing the PTFE additives improves discharge capacity (285 mAh/g at C/10 charge/discharge rate), enhances rate capability (232 mAh/g at 1C charge/discharge rate) and cycling stability of HC as a negative electrode material for potassium-ion batteries that has been tested in both potassium half-cell and potassium-ion full cell configurations.

Keywords

• Hard carbon
• Electrode materials
• Negative electrode
• Potassium-ion batteries
• Synthesis