A fluoroxalate cathode material for potassium-ion batteries with ultra-long cyclability

Abstract

Potassium-ion batteries are a compelling technology for large scale energy storage due to their low-cost and good rate performance. However, the development of potassium-ion batteries remains in its infancy, mainly hindered by the lack of suitable cathode materials. Here we show that a previously known frustrated magnet, KFeC 2 O 4 F, could serve as a stable cathode for potassium ion storage, delivering a discharge capacity of~112 mAh g −1 at 0.2 A g −1 and 94% capacity retention after 2000 cycles. The unprecedented cycling stability is attributed to the rigid framework and the presence of three channels that allow for minimized volume fluctuation when Fe 2+ /Fe 3+ redox reaction occurs. Further, pairing this KFeC 2 O 4 F cathode with a soft carbon anode yields a potassium-ion full cell with an energy density of~235 Wh kg −1 , impressive rate performance and negligible capacity decay within 200 cycles. This work sheds light on the development of low-cost and high-performance K-based energy storage devices.

Organic Electrode Materials for Non-aqueous K-Ion Batteries

“…Given their outstanding energy density and long cycling life, LIBs are widely used in portable electronic equipment, electric vehicles, and large-scale energy storage [1]. However, with the rapidly increasing market demand, the low abundance of lithium resources drives researchers to focus on batteries consisting of earth-abundant elements, such as sodium [2,3], potassium [4,5], and aluminum [6,7]. K-ion batteries (KIBs) have attracted remarkable attention owing to their unique advantages, which make them promising supplements or alternatives for LIBs compared with other metalion batteries.…”

A novel low-cost and environment-friendly cathode with large channels and high structure stability for potassium-ion storage

“…3b). The polarization of 0.3-0.4 V in KFOS cathode is relatively low compared with other KIB cathodes [24,46]. Reversible discharge capacities of around 85, 70, 64, 58 and 54 mA h g −1 were obtained at 100, 200, 300, 400, and 500 mA g…”

“…Our group has previously reported the synthesis and electrochemical study on KFeC 2 O 4 F [24]. Compared with it, the current study exhibits following features: first, with the aim of using oxalate to obtain iron(II) compound in sulfate system, a mixed polyanionic compound was successfully obtained, which provids new synthesis routine in the preparation of iron(II) compound.…”

“…In comparison, the development of ideal cathode materials, such as Prussian blue analogues (PBAs), oxides, polyanions, and organics [17][18][19][20][21][22] are sluggish. For instance, despite of enormous investigations on PBAs, of which the three-dimensional (3D) open framework structure is promising for K-ion storage, the preparation of defect-free and water-free PBAs is difficult, which deteriorates the electrochemical performance of PBAs in terms of kinetics, Coulombic efficiency (CE), and cycling life [23][24][25][26]. tracted more attention owing to their favorable working potentials, rigid structural frameworks for K ion movement and high stability against organic solvents.…”

Covalent Organic Frameworks for Next‐Generation Batteries

“…However, the radius of potassium ions (1.38 Å) is larger than that of lithium ions (0.76 Å) and sodium ions (0.98 Å). [54,55] The obstruction of the K + transmission channel will cause the electrochemical performance of PIBs to be unsatisfactory. Most inorganic electrode materials have excellent performances in LIBs and SIBs, but the electrochemical performance of PIBs is not very remarkable.…”