Sol-Gel Synthesis of Nanostructured Li₂FeSiO₄/C as Cathode Material for Lithium Ion Battery

Abstract

Nanostructured Li 2 FeSiO 4 /C composites have been successfully synthesized by adopting polyethylene glycol (PEG) as the surfactant and L-ascorbic acid as the carbon additive, using a sol-gel method based on the acid-catalyzed hydrolysis/condensation of tetraethoxysilane (TEOS). The Li 2 FeSiO 4 /C nanocomposites possess dispersed spherical particles (∼50 nm) with narrow particle size distribution, embedded in a continuous carbon matrix. The Li 2 FeSiO 4 /C nanocomposites deliver first discharge capacity of 138.2 mAhg −1 at C/16 and maintain at about 130.4 mAhg −1 after 40 cycles at various rates at room temperature, which outperform those of Li 2 FeSiO 4 /C samples synthesized without PEG. The electrochemical performances of Li 2 FeSiO 4 /C were largely enhanced after the introduction of PEG due to the following two aspects. On one hand, the smaller particle size facilitated the shorter diffusion length for lithium ions; On the other hand, the more continuous carbon film coated on the particle surface enhanced the electronic conductivity of the nanocomposites and restrained the side reaction occurring at the electrode-electrolyte interface.

Insight into cobalt-doping in Li2FeSiO4 cathode material for lithium-ion battery

“…11, it is obvious that the Co-doped LFS/C electrode shows a much lower charge-transfer resistance. Furthermore, Li þ ion diffusion in the cathode materials can be calculated from the relationship between Z 0 and the reciprocal square root of the lower angular frequencies (u À1/2 ) [18,49]. Table 4 lists the Li þ ion diffusion coefficient for both samples.…”

Synthesis of Li 2 FeSiO 4 /carbon nano-composites by impregnation method

“…To overcome these severe issues, many attempts have been made in the literature, including micro-nano architecturing [23][24][25] , super-valence dopping 26,27 , incorporation of lithium ion 28,29 or electron conductive matrix 30 , non-stoichiometry [31][32][33] and carbon coating 5,[34][35][36][37][38][39][40][41][42][43][44] . Among these methods, carbon coating is the most wide-spread one.…”

“…Carbon or carbon-containing compounds added to the precursors or to the intermediate mixtures usually protect Fe 2+ from oxidation, inhibits the grain growth and improves the electronic conductivity. 45 Up to now, various carbon or carbon precursors, such as poly(vinyl-pyrrolidone) 46 , P123 polymer 36 , saccharides 34,38,41,[47][48][49][50][51] , L-ascorbic acid 35 , citric acid 37,39,40,51 , multiwall carbon nanotubes 37,52 , phenolic resin 53 etc., have been reported to prepare Li 2 FeSiO 4 /C composites. However, besides the few reports on hydrothermal 41,51 , solvothermal 5 and evaporation-induced self-assembly methods 36 , sol-gel and solid state reaction are the two most commonly used methods to prepare Li 2 FeSiO 4 /C composites.…”

FeF3 microspheres anchored on reduced graphene oxide as a high performance cathode material for lithium ion batteries

“…The lithium diffusion coefficients (D Li ) of bare FeF 3 , FeF 3 /r-GO1.7, and FeF 3 /r-GO11 were calculated from the Warburg region using Eq. (1) [44,45].…”