Building a Long-Lifespan Aqueous K-Ion Battery Operating at −35 °C

Abstract

Aqueous potassium-ion batteries (AKIBs) are promising low-cost and high-safety candidates for large-scale energy storage applications. However, most AKIBs can only operate above −20 °C with a short lifespan at low temperatures (8−300 cycles at −20 °C) owing to the high freezing point of KCF 3 SO 3 -based electrolytes and severe electrode dissolution. Here, we developed an AKIB consisting of K 1.55 Fe[Fe-(CN) 6 ] 0.95 •1.03H 2 O/10 m KCF 3 COO/3,4,9,10-perylenetetracarboxylic diimide. The newly proposed 10 m KCF 3 COO electrolyte has a low freezing point (−35.5 °C) owing to a large H-bond breakage degree and a high average ice formation energy. Both electrodes exhibit low solubility in the 10 m KCF 3 COO electrolyte. As a result, the full cell delivers high energy density (56.3 Wh kg −1 at 25 °C, 41.9 Wh kg −1 at −35 °C) and a long low-temperature lifespan (87.5% capacity retention over 1000 cycles at −35 °C). This work marks a milestone development of AKIBs for low-temperature applications.

Recent advances in rational design for high-performance potassium-ion batteries

“…The problem of a high freezing point often exists in aqueous electrolytes. More recently, Jiang et al 644 found that the N ( r ) values of 10 M KCF 3 COO and 10 M KCF 3 SO 3 electrolytes were 1.27 and 1.39, respectively, indicating that the degree of hydrogen bond breaking in the former was higher than that in the latter (Fig. 70f).…”

Deciphering the Interface Failure Mechanism for Aqueous Na-Ion Batteries at Low Temperatures

“…Due to the mounting demands for renewable energy and the development of grid-scale energy, aqueous Na-ion batteries (ANIBs), which possess the merits of inherent safety, abundant reserves, and high ionic conductivity, have been regarded as promising alternatives in the era of organic batteries. − However, with water as the solvent, conventional dilute aqueous electrolytes restrict the multiscenario and all-climate applications of ANIBs, which have been naturally imputed to the high activity of water molecules. − Along this line, varied research has focused on the modification of aqueous electrolytes and has developed numerous approaches to widen the electrochemical window and lower the freezing points, such as the introduction of the “water-in-salt” concept − and organic additives. − Besides, the artificial solid electrolyte interphase (SEI) layer could kinetically prevent water molecules from penetrating the electrode materials, thus inhibiting water electrolysis. , Nevertheless, the effects of an interface toward the low-temperature performance of ANIBs remain elusive, which is worth exploring in this field. In organic batteries, the high interfacial resistance linking to desolvation energy and SEI begets battery failure at low temperatures, where the verified failure mechanisms have been employed to guide the optimization of solvation structures, thus addressing the poor low-temperature performance. , Compared with organic systems, ANIBs mostly derive a thin and unstable SEI, yet the distributions of charge carriers and water molecules in the inner Helmholtz plane (IHP) still need much attention at low temperatures.…”