Ternary Ionogel Electrolytes Enable Quasi‐Solid‐State Potassium Dual‐Ion Intercalation Batteries

Abstract

A dual‐ion battery (DIB) is an emerging technology destined for use in stationary energy storage applications. Most DIB prototypes use expensive salt‐concentrated liquid electrolytes to ensure sufficient ion supply and an electrochemical stability window beyond 4.5 V, which is required for anion intercalation in graphite. Herein, the design of a compact quasi‐solid‐state potassium‐based DIB is introduced using ternary ionogel electrolytes (t‐IGEs) prepared from a potassium salt, an ionic liquid, and a poly(ionic liquid). Among a series of combinations, the t‐IGE with optimum mechanical property, thermal stability (>200 °C), and electrochemical performance consists of 30% salt, 28% ionic liquid, and 42% poly(ionic liquid). With ionic conductivity ranging from 0.1 to 1 mS cm−1 at 30–100°C and an electrochemical stability window within 0.5–5.0 V versus K+/K, the t‐IGE is suited for practical MoS2–graphite KDIBs. Infusing the ionogel in plain‐weave glass fiber fabrics (≈40 μm thick) further enables the design of more compact KDIBs in which a significant reduction (≈64%) in electrolyte thickness is achieved. The cells are able to deliver specific capacities varying from 80 to 25 mAh g−1 at 10 to 160 mA g−1, with CEs ranging from ≈90% to 100%.

Keywords

• dual-ion batteries
• graphite
• ionogel electrolytes
• potassium
• transition metal dichalcogenide