Solvation Structure Modulation of High‐Voltage Electrolyte for High‐Performance K‐Based Dual‐Graphite Battery

Abstract Due to the advantages of dual‐ion batteries (DIBs) and abundant resources, potassium‐based dual‐carbon batteries (K‐DCBs) have wide application prospects. However, conventional carbonate ester‐based electrolyte systems have obvious drawbacks such as poor oxidation resistance and difficulty in sustaining the anion intercalation process at high voltages, which seriously affect the capacity and cycle performance of K‐DCBs. Therefore, a rational design of more efficient novel electrolyte systems is urgently required to realize high‐performance K‐DCBs. Herein, a solvation structure modulation strategy for the K‐DCB electrolyte systems is reported. Consequently, substantial K⁺ ion storage improvement at the graphite anode and enhanced bis(fluorosulfonyl)imide anion (FSI⁻) intercalation capacity at the graphite cathode are successfully realized simultaneously. As a proof‐of‐concept, the assembled K‐DCB exhibited a discharge capacity of 103.4 mAh g⁻¹, and after 400 cycles, ≈90% capacity retention is observed. Moreover, the energy density of the K‐DCB full cell reached 157.6 Wh kg⁻¹, which is the best performance in reported K‐DCBs till date. This study demonstrates the effectiveness of solvation modulation in improving the performance of K‐DCBs.