Regular Mesoporous Structural FeSe@C Composite with Enhanced Reversibility for Fast and Stable Potassium Storage

Abstract

Due to the superior theoretical capacity, impressive operating potential, and environmental benignity, metal selenides as the promising candidates have attracted extensive interest in potassium-ion batteries (KIBs). However, structure collapse of the electrode and sluggish reaction kinetics restrict their application in KIBs owing to the volume expansion of metal selenides and the large radius of K+. Herein, we rationally select metal–organic framework (MOF) iron 1,3,5-benzenetricarboxylate (MIL-100­(Fe)) as the precursor on account of its microporous opening windows and mesoporous cages, which well-confined selenium (Se) and fabricated mesoporous structural FeSe@C (NFC) successfully. The mesoporous structural NFC electrode achieved 310 mA h g–1 at 500 mA g–1 over 1000 cycles with 98% coulombic efficiency and delivered excellent rate capacity (276 mA h g–1 at 1000 mA g–1 and 254 mA h g–1 at 2000 mA g–1), which could be attributed to the large surface area and mesoporous structural composite along with carbon framework coating. It can also be concluded that the pseudocapacitive contribution accelerates K+ transport and enable faster kinetics. Significantly, in situ X-ray diffraction (XRD) analysis revealed that the conversion reaction mechanism of FeSe (FeSe + 2K+ ↔ Fe + K2Se) occurs on reduction and oxidation reversibly. The superior electrochemical performance exhibits the great potential of the FeSe@C composite as a promising anode material for KIBs.

Recent advances in Fe-based metal–organic framework derivatives for battery applications

“…153,154 Unfortunately, the radius of the potassium ion (0.138 nm) is much larger than that of the lithium ion (0.076 nm), which makes it difficult for potassium ions to embed and dislodge in electrode materials. 155 Therefore, the development of a new high-capacity electrode material which can be suitable for PIBs has become a research focus. In order to solve the above problems, Fe-MOF-derived transition metal compounds have attracted the attention of researchers, once again, in order to synthesize and design electrode materials with excellent performance, thus accelerating the practical application of PIBs.…”

“…9b). 155 Owing to the special mesoporous structure, highly dispersed selenides and protective carbon-based coatings obtained using an Fe-MOF, the design and preparation of this nanomaterial effectively improved the electrochemical performance of PIBs. In short, the FeSe@C electrode overcame the volume fluctuation of PIBs, provided abundant diffusion space for potassium ions, and had excellent long-period stability as well as excellent rate performance in battery testing, indicating the potential of Fe-MOF derivatives as high-performance electrodes.…”

Nanostructured metal selenides as anodes for potassium-ion batteries

“…Through the extended gas-phase selenization method, FeSe nanoparticles were encapsulated inside the carbon matrix, and FeSe@C retained the framework structure of the MIL-100(Fe) precursor. 90 By exploiting the good adsorption properties of biomass materials, Zeng and co-workers reported an ultrasmall few-layer MoSe 2 nanoparticle inserted N, P co-doped bio-carbon (MoSe 2 /NP-C) through a simple gas-phase selenization. 83 Chlorella was firstly used as the adsorbent to absorb the Mo-containing precursor, and then chlorella was converted into spherical bio-carbon, while Mo ions were transferred into MoSe 2 during the selenization process.…”

In situ atomic‐scale observation of size‐dependent (de)potassiation and reversible phase transformation in tetragonal FeSe anodes

“…46 Considering the low cost, nontoxic nature, and abundance of reserves in the earth, anode materials based on iron selenides like FeSe 2 and FeSe have been found to deliver stable capacities in PIBs. 47,48 Deng et al prepared an interconnected threedimensional (3D) porous carbon skeleton with FeSe nanoparticles, which helped buffer volume expansion and promoted fast and efficient ionic transport, resulting in improved performance. They also regarded K 2 Se as a product of the potassiation reaction.…”

“…Interestingly, the conductivity of Se (1 × 10 −5 S m −1 ), a group VI element, is several orders of magnitude higher than that of S (5 × 10 −30 S m −1 ) 46 . Considering the low cost, nontoxic nature, and abundance of reserves in the earth, anode materials based on iron selenides like FeSe 2 and FeSe have been found to deliver stable capacities in PIBs 47,48 . Deng et al prepared an interconnected three‐dimensional (3D) porous carbon skeleton with FeSe nanoparticles, which helped buffer volume expansion and promoted fast and efficient ionic transport, resulting in improved performance.…”