Abstract
The porous carbon matrix is widely recognized to be a promising sulfur reservoir to improve the cycle life by suppressing the polysulfide dissolution in lithium sulfur batteries (LSB). Herein, we synthesized mesocellular carbon foam (MSUF-C) with bimodal mesopore (4 and 30 nm) and large pore volume (1.72 cm2/g) using MSUF silica as a template and employed it as both the sulfur reservoir and the conductive agent in the sulfur cathode. Sulfur was uniformly infiltrated into MSUF-C pores by a chemical solution deposition method (MSUF-C/S CSD) and the amount of sulfur loading was achieved as high as 73% thanks to the large pore volume with the CSD approach. MSUF-C/S CSD showed a high capacity (889 mAh/g after 100 cycles at 0.2 C), an improved rate capability (879 mAh/g at 1C and 420 mAh/g at 2C), and a good capacity retention with a fade rate of 0.16% per cycle over 100 cycles.
Highlights
The porous carbon matrix is widely recognized to be a promising sulfur reservoir to improve the cycle life by suppressing the polysulfide dissolution in lithium sulfur batteries (LSB)
We examined a new type of mesoporous carbon foam as the sulfur reservoir having bimodal mesopores (4 and 30 nm), synthesized with mesocelluer silica foam (MSUF) as a template, referred to as MSUF-C
The MSUF-C chemical solution deposition (CSD) demonstrated a well-balanced feature of large pore size being beneficial for sulfur loading and small pore size having a merit of polysulfide confinement
Summary
MSUF-C/S CSD achieved the high loading density of active sulfur material and simultaneously was successfully inhibited the polysulfide dissolution in comparison with other samples, because sulfur was uniformly infiltrated into small pores of MSUF-C with no defect and no deformation by chemical solution deposition method, as can be seen in TEM and SAXS result. In comparison with the simple ball-mixing and the melt diffusion method, the MSUF-C synthesized by CSD-method had less surface defect and structural distortion, and the sulfur was uniformly dispersed in mesopores of MSUF-C, as confirmed by TEM and SAXS analysis. MSUF-C/S CSD resulted in higher capacity, capacity retention and rate capability than other samples and showed enhanced cycle perforamnce by suppressing the polysulfide dissolution This result can be attributed to the fact that the sulfur was uniformly infiltrated into even small pores of MSUF-C by CSD-method. A combination of the MSUF-C with bimodal mesopores and the CSD-method can be a promising solution to achieve a long cycle life and a high rate capability for lithium sulfur batteries
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