Carbon-Free Crystal-like Fe_1–xS as an Anode for Potassium-Ion Batteries

Abstract

Potassium-ion batteries (PIBs) as a new electrochemical energy storage system have been considered as a desirable candidate in the post-lithium-ion battery era. Nevertheless, the study on this realm is in its infancy; it is urgent to develop electrode materials with high electrochemical performance and low cost. Iron sulfides as anode materials have aroused wide attention by virtue of their merits of high theoretical capacities, environmental benignity, and cost competitiveness. Herein, we constructed carbon-free crystal-like Fe 1−x S and demonstrated its feasibility as a PIB anode. The unique structural feature endows the prepared Fe 1−x S with plentiful active sites for electrochemical reactions and short transmission pathways for ions/electrons. The Fe 1−x S electrode retained capacities of 420.8 mAh g −1 after 100 cycles at 0.1 A g −1 and 212.9 mAh g −1 after 250 cycles at 1.0 A g −1 . Even at a high rate of 5.0 A g −1 , an average capacity of 167.6 mAh g −1 was achieved. In addition, a potassium-ion full cell is assembled by employing Fe 1−x S as an anode and potassium Prussian blue as a cathode; it delivered a discharge capacity of 127.6 mAh g −1 at 100 mA g −1 after 50 cycles.

A novel strategy for encapsulating metal sulfide nanoparticles inside hollow carbon nanosphere-aggregated microspheres for efficient potassium ion storage

“…From the second cycle onwards, the CV curves of HCA-FeS microspheres revealed peaks related to the conversion reaction with potassium ions and formation/deformation of the SEI layer. 59 The CV curves of FeS microspheres are shown in Fig. S14, † where similar peaks were observed when compared with those of HCA-FeS microspheres.…”

“…During the initial cathodic sweep, the CV curve of HCA-FeS microspheres exhibited a broad peak until 1.0 V and an explicit peak at 0.8 V, which can be attributed to the intercalation of potassium ions, conversion reaction of Fe 1− x S with potassium ions and formation of the SEI layer, respectively. 50,59 For the initial charge process, a broad peak was observed at 1.5 V, which corresponded to the conversion reaction to form K x FeS 2 . 45,60 This result is in line with many previous reports on the use of iron sulfide materials as PIB anodes, where potassium iron sulfide materials are formed during the charge process.…”

Synthesis of CoSe2 reinforced nitrogen-doped carbon composites as advanced anodes for potassium-ion batteries

“…15,16 Unfortunately, the conversion reaction and/or the alloying reaction of MCs with potassium ions is generally accompanied by the breaking and reorganization of chemical bonds 17,18 and at the same time MCs undergo a huge volume change, which leads to the structural collapse of electrode materials. 19,20 To this end, constructing composites is proposed as an effective strategy to develop high performance anodes for PIBs, which enables a combination of mutual advantages of all compositions while compensating for the shortcomings of each component. 21,22 For example, Xu et al synthesized heterogenous MoSe 2 /N-doped carbon nanoarrays on the surface of rGO (MoSe 2 @C/rGO) as high-performance PIB anodes.…”

A Stabilized Polyacrylonitrile-Encapsulated Matrix on a Nanolayered Vanadium-Based Cathode Material Facilitating the K-Storage Performance

“…Unfortunately, there are still plentiful challenges in the large-scale commercial manufacture of PIBs on account of the large size effect of K ions (1.38 Å) much more than that of Li ions (0.76 Å). Until now, many cathode materials of PIBs have been proposed mainly including Prussian blue and its analogues, layered transitional metal oxides, polyanionic compounds, and organic cathodes. − A number of late-model cathode materials such as some 2D or 3D metal organic frameworks and covalent organic frameworks were also applied as cathode materials of PIBs. − Among them, layered potassium vanadium oxides have inspired further development because of their superior air stability, suitable K + transport channel, and high redox potential with easy fabrication, mainly including K 0.486 V 2 O 5 , K 0.5 V 2 O 5 , K 0.83 V 2 O 5 , K 2 V 8 O 21 , K 2 V 3 O 8 , and so on. , For instance, the typical vanadium-based metal oxide (K 0.486 V 2 O 5 ) has been regarded as one of the competitive alternatives with a high average potential of 3.2 V together with a high K-ion theoretical specific capacity of ∼120 mAh g –1 . Nevertheless, the larger K + makes the volume variation of PIBs in the charge/discharge processes more violent than other alkali metal ions, resulting in the collapse of the crystal structure and even delivering the powdering of the electrodes. − Meanwhile, the lower transfer capability of K + in the bulk phase of the electrode material restricts its high-rate performance.…”