Uncovering the Role of Organic Species in SEI on graphite Towards Fast K+ Transport and Long-life Potassium-ion Batteries

Abstract

The performance of potassium ion batteries (PIBs) using graphite anode is highly dependent on the composition of solid electrolyte interphase (SEI) that include both organic and inorganic species. Currently, most researches focus on constructing an inorganic-rich SEI, whereas the critical role of organic components is barely understood and thus hinders the rational regulation of SEI chemistry. Herein, tailored SEI composition with controllable organic/inorganic ratios on graphite surface has been obtained through simply adjusting the temperatures, and a series of experiments have been conducted to understand their ionic transport capabilities and stability using Prussian white/graphite full cells. The organic component is identified crucial in enhancing the kinetics. Consequently, the full cell with organic-rich SEI (such as -(CH2CH2O)n-) exhibits good rate capability, whereas the full cell with inorganic-rich SEI (such as KF) demonstrates excellent cycling performance. In contrast, the full cell with an organic-inorganic balanced SEI can provide fast K+ transport capabilities and good mechanical stability synergistically, thereby achieving good rate performance and cycling stability. Our research reveals the critical role of organic components in SEI to optimize K+ storage performance, which provides valuable guidance for the rational design of SEI and offers significant potential for the development of high performance PIBs.