6.0 V High-Voltage and Concentrated Electrolyte toward High Energy Density K-Based Dual-Graphite Battery

K-based dual-carbon batteries (K-DCBs) integrate the advantages, including high-voltage, low-cost, and environmentally friendliness of dual-ion batteries (DIBs), and large abundance of K, thus attracting much attention in large-scale energy storage application. However, most currently used electrolytes based on KPF(6)and carbonate solvents commonly suffer from poor oxidation potential (<4.4 V vs Li/Li+) and low electrolyte concentration (<1 m), which limit the cycling stability and energy density of K-DCBs. Herein, after a matching behavior study of various electrolyte solvents with potassium salts, a concentrated electrolyte is developed by successfully dissolving 5.2 m potassium bis(fluorosulfonyl)imide into tetramethylene sulfone. This high-concentration electrolyte exhibits advantages: 1) high oxidation potential that enhances intercalation reversibility and capacity of FSI(-)anions; 2) improved K(+)storage at graphite anode; 3) dramatically increased energy density of K-DCB. A proof-of-concept K-ion dual-graphite battery based on this high-concentration electrolyte displays a discharge capacity of 83.4 mAh g(-1)at 100 mA g(-1), and negligible capacity fading after 300 cycles. Furthermore, considering both the electrolyte and electrode materials, energy density of such K-DCB reaches approximate to 130 Wh kg(-1), the best performance of K-DCBs among previously reported research.