Synthesis of Mesoporous Fe₂SiO₄/C Nanocomposites and Evaluation of Their Performance as Materials for Lithium‐Ion Battery Anodes

Abstract

The first kind of mesoporous Fe 2 SiO 4 /C nanocomposites (MFS-1) were synthesized from the nano-SiO 2 with a surface area of 137 m 2 ⋅g À 1 and the second kind of mesoporous Fe 2 SiO 4 /C nanocomposites (MFS-2) were prepared from the nano-SiO 2 with a surface of 325 m 2 ⋅g À 1 . XRD results indicate that α-Fe 2 SiO 4 crystal phase appear in the two samples. SEM proves that the particle size of MFS-2 (30-40 nm) is smaller than that of MFS-1 (40-60 nm). TEM further proves Fe 2 SiO 4 nanoparticles are homogeneously dispersed in the carbon networking of MFS-2.Pore structure analysis reveals that the specific surface area of MFS-2 (136 m 2 ⋅g À 1 ) is evidently larger than that of MFS-1 (116 m 2 ⋅g À 1 ), revealing the pore properties of mesoporous Fe 2 SiO 4 /C nanocomposites can be well controlled by using silica with different surface area. The above characters make MFS-2 exhibit a high initial reversible capacity of 667 mAh⋅g À 1 at 0.1 C, excellent rate capability (282 mAh⋅g À 1 at 10 C) and improved cycling stability (606 mAh⋅g À 1 at 1 C after 100 cycles).

Microsized fayalite Fe2SiO4 as anode material: the structure, electrochemical properties and working mechanism

“…First discharge curve has plateau at around 1.3 V, while on subsequent cycling charge/discharge curves transform to decline lines with just a small residual of the plateau. This feature is previously observed in cycling performances not only for Fe 2 SiO 4 but also for other anode materials [1,5,9]. The initial irreversible capacity is a phenomenon that is essentially attributed to the reduction of the electrolyte through the formation of a solid electrolyte interphase (SEI) and/or from irreversible lithium insertion into special positions [2,10].…”

“…Based on these findings, Guo et al presumed the same type conversion reactions for Fe 2 SiO 4 : Fe 2 SiO 4 + 4Li + +4e -= 2Fe 0 +Li 4 SiO 4 on first discharge, and xFe 0 +Li 4 SiO 4 + 4e -4Li + +4e -= Fe x SiO y on subsequent charge/discharge [6]. The electrochemical properties of fayalite/carbon composites were systematically reported in several papers [4][5][6][7][10][11][12]. Typically, first discharge is much longer than the subsequent charges/discharges and the capacities vary but are often above theoretical value (between 500 -700 mAhg -1 at 0.1C).…”

“…Since the conversion reaction starts from the surface of the particle (fast Li surface diffusion) and move inward (slow lithium diffusion), it is size dependent. It can be concluded that in the case of Fe 2 SiO 4 , unlike Co 2 SiO 4 [9], good electrochemical performances can only be expected for nanoparticle powder [5].…”

“…Fayalite occurs as a common member of the olivine group of minerals, and also as a waste product (slag) during the manufacturing of copper [3]. Recently, fayalite phase is considered for use as an anode material in lithium-ion batteries [4][5][6][7].…”

Investigation of self-consistent site-dependent DFT + U effect on electronic band structure and optical properties of SiFe2O4 spinel

“…Owing to the possibility of accommodating earths abundant transition metals in different oxidation states at the O h and T d sites, spinels such as the CuFe 2 O 4 , GaZn 2 O 4 , CuCo 2 O 4 and SnMg 2 O 4, offer an excellent opportunities for designing many technological applications which include: transparent conducting oxides (TCOs), [7][8][9][10][11], humidity sensors, magnetic materials for spintronics and storage devices, redox materials for solar-thermal water splitting, high surface-reactivity catalysts for water-gas shift reactions, electrodes in lithium-ion as well as sodium-ion batteries, and hydrogen generation for microbial systems [12][13][14][15][16]. In a 'normal' XM 2 O 4 spinel-type oxide, all X cations occupy the O h sites while the M cations occupy T d sites, whereas, in an 'inverse' spinel-type, the O h sites are shared equally by X and M cations with the T d sites occupied only by X cations [17].…”