Electrolyte Salt Chemistry Enables 3D Nitrogen and Phosphorus Dual-Doped Graphene Aerogels for High-Performance Potassium-Ion Batteries

Potassium-ion batteries (PIBs) have attracted tremendous attentions for scalable electrical energy storage owing to the abundant K resources. Heteroatom co-doped hard carbon is considered to be a reliable material to boost ion transport and provide active sites for reversible potassium storage. Herein, N/P dual-doped 3D graphene aerogels (NPGAs) with hierarchical pores, enlarged interlayer distance, and high doping level are successfully synthesized, which exhibit outstanding electrochemical performance for PIBs. A detailed comparative study found that promoted coulombic efficiency, improved specific capacity (507 mAh g(-1) at 100 mA g(-1) after 100 cycles) and excellent cycle performance (106 mAh g(-1) at 5000 mA g(-1) after 3000 cycles) can be reached by replacing KPF6 with potassium bis(fluorosulfonyl)imide (KFSI). Further kinetic analysis reveals that NPGAs present more capacitive behavior of K-ion, low resistance, and fast K-ion conductivity by virtue of the advanced solid electrolyte interphase (SEI) film formed in KFSI-EC/DEC electrolyte. Ex situ XPS, SEM, and TEM all confirm a physical flexible, chemical stable, and inorganic SEI layer formed on the surface of the electrode. In general, this work promotes a deep understanding of the mechanism of potassium storage and provides more opportunities for practical PIBs.