Highly Concentrated KTFSI : Glyme Electrolytes for K/Bilayered‐V₂O₅ Batteries

Abstract

Highly concentrated glyme‐based electrolytes are friendly to a series of negative electrodes for potassium‐based batteries, including potassium metal. However, their compatibility with positive electrodes has been rarely explored. In this work, the influence of the molar fraction of potassium bis(trifluoromethanesulfonyl)imide dissolved in glyme on the cycling ability of K/bilayered‐V2O5 batteries has been investigated. At high salt concentration, the interaction between K+ ions with the glyme is strengthened, leading to a limited number of free glyme molecules. Therefore, the anodic decomposition of the electrolyte solvent, as well as the dissolution of the Al current collectors, is effectively suppressed, resulting in the improved cycling ability of the K/bilayered‐V2O5 cells. In these cells, the positive electrode active material exhibits reversible capacities of 93 and 57 mAh g−1 at specific current densities of 50 and 1000 mA g−1, respectively. After 200 charge‐discharge cycles at 500 mA g−1, the cell retains 94 % of the initial capacity. The promising rate performance and capacity retention demonstrate the importance of proper electrolyte engineering for the K/bilayered‐V2O5 batteries, and the good compatibility of highly concentrated glyme‐based electrolytes with positive electrode materials for potassium batteries.

The Features and Progress of Electrolyte for Potassium Ion Batteries

“…Recently, Komaba and co‐workers [ 27 ] proved that the aluminum collector have a smooth surface when they are circulated in a concentrated KFSI–DME electrolyte (7 mol kg −1 ), and no obvious current was observed in the cyclic voltammetry test. Liu et al [ 59 ] discovered a similar effect in another concentrated electrolyte (KTFSI–DME). They pointed out that with salt concentration increase, the interaction between K + and TFSI − will be enhanced and the free solvent molecules reduced, so a high concentrated electrolyte usually has a good compatibility with the aluminum current collector.…”

“…Due to the solvation effect of concentrated electrolyte, a stable interface can be formed and the corrosion of collector can be retard. [ 27,59 ] Moreover, the binary‐salts electrolyte has also attracted the attention of researchers due to low viscosity and cost. [ 60,61 ]…”

Alkoxy-functionalized ionic liquid electrolytes: understanding ionic coordination of calcium ion speciation for the rational design of calcium electrolytes

“…Having demonstrated the plating and stripping of Ca, we used the [Ca(BH 4 ) 2 ] 0.05 [N 07 TFSI] 0.95 electrolyte to assemble a proof-of-concept rechargeable Ca battery coupling a Ca metal anode and a V 2 O 5 aerogel cathode. The bilayered-V 2 O 5 has been used as the cathode host materials for various cations, e.g., Li + , 51 Na + , 52 K + , 53 Zn 2+ , 54 Mg 2+ ions, 31 and its ability has also been successfully demonstrated for reversible intercalation/ de-intercalation of Ca 2+ ion. [55][56][57] However, compared to monovalent cations, multivalent ions suffer from high migration energy barriers.…”

“…The V 2 O 5 aerogel cathode material was prepared according to the reported microwave driven reaction. 52,53 The cathodes were composed of 70 wt% active material, 20 wt% carbon black (Super C65, IMERYS), and 10 wt% polyacrylic acid (Sigma-Aldrich, average M v of B1 250 000) binder with aluminum foil current collectors. The average mass loading of active material was around 1.4 mg cm À2 .…”

Computational Screening of the Physical Properties of Water‐in‐Salt Electrolytes**

“…Greener and lower‐cost alternatives to fluorinated compounds would also be preferable; in order to fulfil this objective WiS based on the acetate anion instead of TFSI were also proposed, [28–30] showing further the versatility of this family of electrolytes. Other solvents, such as glymes, are also widely investigated for the development of superconcentrated electrolytes [31,32] …”