Interfacial tuning of the graphite anode for potassium ion intercalation in a wide temperature range

Abstract

The reversible intercalation of potassium ion on the graphite anode is one of the shining advantages for potassium ion batteries (PIBs). However, graphite anode suffers from capacity loss and cycling instability due to the increased desolvation energy and the slow transport of ions through the solid electrolyte interface (SEI) during low-temperature operation. In addition, graphite shows instability at high temperature due to the unstable SEI caused by electrolyte decomposition. To address these issues, our rational design is to tune an SEI with fast kinetics and stable property by introducing a weakly solvated electrolyte, 1,2-diethoxyethane, and a fluorinated additive, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether. The optimized electrolyte not only reduces the desolvation energy and increases the ion conductivity of the SEI at low temperatures but also forms a uniform SEI at high temperatures, enabling stable cycling over a wide temperature range. Impressively, at −5 °C, the specific capacity of the graphite anode reached 230 mA h g⁻¹ with the capacity retention rate of 85.8% to room temperature. At 45 °C, it obtained a reversible specific capacity of 273 mA h g⁻¹ and stabilized for 200 cycles. In addition, the full cells assembled with 2,3-dimethylene-3,4,9,10-tetracarboxydianhydride (PTCDA) as the cathode and graphite as the anode delivered promising performance at wide temperature. This work provides an advanced insight into wide-temperature graphite-based potassium ion batteries.