Ultrastable Graphite‐Potassium Anode through Binder Chemistry

Abstract Graphite with abundant reserves has attracted enormous research interest as an anode of potassium‐ion batteries (PIBs) owing to its high plateau capacity of 279 mAh g⁻¹ at ≈0.2 V in conventional carbonate electrolytes. Unfortunately, it suffers from fast capacity decay during K⁺ storage. Herein, an ultrastable graphite‐potassium anode is developed through binder chemistry. Polyvinyl alcohol (PVA) is utilized as a water‐soluble binder to generate a uniform and robust KF‐rich SEI film on the graphite surface, which can not only inhibit the electrolyte decomposition, but also withstand large volume expansion during K⁺‐insertion. Compared to the PVDF as binder, PVA‐based graphite anode can operate for over 2000 cycles (running time of 406 days at C/3) with 97% capacity retention in KPF₆‐based electrolytes. The initial Coulombic efficiency (ICE) of graphite anode is as high as 81.6% using PVA as the binder, higher than that of PVDF (40.1%). Benefiting from the strong adhesion ability of PVA, a graphite||fluorophosphate K‐ion full battery is further built through 3D printing, which achieves a record‐high areal energy of 8.9 mWh cm⁻² at a total mass loading of 38 mg cm⁻². These results demonstrate the important role of binder in developing high‐performance PIBs.