Solution-processable design strategy for a Li₂FeSiO₄@C/Fe nanocomposite as a cathode material for high power lithium-ion batteries

Abstract

Li2FeSiO4@C/Fe nanocomposites have been synthesized by solution-processable approaches, which exhibit a superior rate performance as a cathode material for lithium-ion batteries.

Soft-template construction of three-dimensionally ordered inverse opal structure from Li2FeSiO4/C composite nanofibers for high-rate lithium-ion batteries

“…As a result, the 3DOM-LFS/C-NF cathode may deliver a higher energy than the 3DOM-LFS/C cathodes at high C-rates. Although the rate performance is similar to our previous LFS/Fe 7 SiO 10 /C or LFS/Fe/C nanocomposites, 7,8 the apparent specific capacity of the present 3DOM-LFS/C-NF cathode is higher because of the decreasing contents of the inactive phases such as Fe and Fe 7 SiO 10 in the electrodes.…”

“…It should be pointed out that Li 2 FeSiO 4 is a promising cathode material that may undergo the extraction/insertion mechanism of two lithium ions per formula unit, which is a multielectron charge transfer (Fe 2+ /Fe 4+ redox couple) process, thus leading to the theoretical capacity of 332 mA h g −1 . In our present and previous experiments, 7,8 the discharge capacity of nanostructured LFS was 180-200 mA h g −1 within the voltage window of 1.5-4.5 V in several of the early cycles at 0.1 C (Fig. 6a), corresponding to more than one lithium extraction/ insertion.…”

“…As a result of the self-limited growth, the nanocrystal-amorphous carbon composite retains good thermal stability due to limited Ostwald ripening during the crystal growth process in the temperature range of less than 700 °C. If a higher temperature is further supplied, however, the carbothermal reduction between the LFS and carbon makes LFS nanocrystals dissolve and the carbon phase pyrolyzes, resulting in metallic iron 8 and leading to a collapse of the nanofiber morphology and 3DOM architecture.…”

“…For example, polyanion-type silicate Li 2 FeSiO 4 (LFS) is a typically electrical insulating-oxide as a potential cathode material for LIBs. [4][5][6][7][8][9][10][11][12][13][14] LFS particles (with crystallite size >100 nm) severely suffered from sluggish kinetics due to their insulating character, leading to a poor rate capability. [5][6][7] In a view point of the kinetics of electrode reaction in the LIB, for a lithium storage process it involves not only electron transport but also Li + ion diffusion in solid materials.…”

“…According to the diffusion formula t = L 2 /D (where t is the charge diffusion time, L is the diffusion length, and D is the diffusion coefficient), the decrease in particle size from bulk to nanoscale leads to a reduced ion/electron transport distance and an increased surface area, thereby improving the rate performance. [5][6][7][8][9][10][11][12] However, nanoparticles have introduced new challenges, including higher surface area, low tap density and poor electrical properties due to the higher inter-particle resistance. The high surface area increases the side reaction between active materials and the electrolyte, and suffers from detachment from each other or self-aggregation during expansion/ contraction cycling.…”