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%.
Highlights
Sustainable battery materials and chemistries are required to complement the growing demand for renewable energy from solar farms, wind mills, and hydroelectric power stations which are characterized by either demand fluctuations or periodic supply interruptions.[1]
We report a full-cell KDIB based on MoS2 negative electrode and graphite positive electrode in a ternary ionogel electrolyte (t-IGE) consisting of potassium bis(fluorosulfonyl)imide (KFSI), 1-butyl-1-methylpyrrolidinium bis(fluorosulfonyl)imide (Pyr14FSI), and poly[diallyldimethylammonium bis(trifluoromethanesulfonyl)imide]
Increasing the Pyr14FSI to pDDA-TFSI ratio greatly influenced the mechanical properties and appearance of the ionogel films; while all films remained freestanding after evaporating the acetonitrile solvent, the ionogels with a low pyr14FSI: pDDATFSI ratio (10:90 and 20:80) proved to be rigid and brittle as compared with the films with a higher Pyr14FSI content
Summary
Sustainable battery materials and chemistries are required to complement the growing demand for renewable energy from solar farms, wind mills, and hydroelectric power stations which are characterized by either demand fluctuations or periodic supply interruptions.[1] To keep a balance between supply and demand at all times, the intermittent nature of renewables should be leveled using stationary batteries deploying abundant, inexpensive, and nontoxic materials.[2,3] Current stationary batteries rely heavily on expensive transition metals (e.g., nickel– cadmium or nickel–metal hydride batteries, and vanadium redox centration, type of electrolyte solvent, type of anion in the electrolyte, working temperature, and amount of electrolyte in the cell.[7,8] Reported gravimetric capacities for half-cells generally vary between 80 and 140 mAh gÀ1 with discharge voltages averaging 4.5 V.[6,9] On the basis of these metrics, lithium metal DIBs can be optimized to deliver cell-level energy density and specific energy above 200 Wh LÀ1 and 100 Wh kgÀ1, respectively, better than lead–acid batteries (50–80 Wh LÀ1 or 20–55 Wh kgÀ1) and comparable with Ni–metal hydride batteries (150–220 Wh LÀ1 or 50–70 Wh kgÀ1) or Na–S batteries (150–300 Wh LÀ1 or 80–150 Wh kgÀ1).[6,10] Using graphite as the anion-hosting electrode, a wide selection of materials can be utilized in the negative electrode, which allows for increasingly diverse electrode–
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