Uncovering the role of organic species in the SEI on graphite for fast K+ transport and long-life potassium-ion batteries

The performance of potassium-ion batteries (PIBs) with a graphite anode is highly dependent on the composition of the solid electrolyte interphase (SEI), which includes both organic and inorganic species. Currently, most research focuses on constructing an inorganic-rich SEI, while the critical role of organic components is barely understood, thus hindering the rational regulation of SEI chemistry. Herein, a tailored SEI composition with controllable organic/inorganic ratios on the graphite surface was obtained by simply adjusting the temperature. A series of experiments were conducted to evaluate their ionic transport capabilities and stability using Prussian white/graphite full cells. The organic component was identified as playing a crucial role in enhancing the kinetics. Consequently, the full cell with an organic-rich SEI (such as -(CH2CH2O)n-) exhibited good rate capability, whereas the full cell with an inorganic-rich SEI (such as KF) demonstrated excellent cycling performance. In comparison, the full cell with an organic-inorganic balanced SEI could 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 the SEI for optimizing K+ storage performance, providing valuable guidance for the rational design of SEI and offering significant potential for the development of high-performance PIBs.