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High‐Speed Lithium‐Ion Transfer inside Mesoporous Core–Shell LiFePO 4 /Carbon‐Sphere Cathodes
Author(s) -
Hsu ChunHan,
Liao HsinYi,
Kuo PingLin
Publication year - 2014
Publication title -
energy technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.91
H-Index - 44
eISSN - 2194-4296
pISSN - 2194-4288
DOI - 10.1002/ente.201300163
Subject(s) - mesoporous material , materials science , lithium (medication) , ion , chemical engineering , electrolyte , nanoscopic scale , carbon fibers , electrode , composite number , nanotechnology , analytical chemistry (journal) , chemistry , composite material , chromatography , medicine , organic chemistry , engineering , endocrinology , catalysis , biochemistry
A thin layer of LiFePO 4 was coated onto a mesoporous carbon sphere to obtain a mesoporous core–shell LiFePO 4 /carbon sphere (LFP/MCS) composite, for which the thickness of the nanoscale LiFePO 4 thin shell was approximately 30–50 nm. Meanwhile, pristine LFP and MCS mixed with LFP samples (MCS‐m‐LFP) were prepared for comparison. The significantly larger surface area of LFP/MCS (43–151 m 2 g −1 ) compared with pristine LFP (12 m 2 g −1 ) is derived from the mesoporous carbon framework and thin nanoscale LFP shell. The large surface area of LFP/MCS provides greater surface content between the LiFePO 4 shell and electrolytes, which results in a high charge–discharge rate. Also, this remarkably thin LiFePO 4 cathode shell shortens the diffusion length of lithium ions thereby achieving a high charge–discharge rate for electrode materials. Consequently, under all charge–discharge rates (0.1–20 C ), the specific capacities of LFP/MCS are higher than those of both the pristine LFP and MCS‐m‐LFP. More specifically, at 10 C , LFP/MCS exhibited the excellent rate performance of 82 mAh g −1 , compared to 25 and 41 mAh g −1 for LFP and MCS‐m‐LFP, respectively. Furthermore, the discharge capacity for LFP/MCS at the high discharge rate of 20 C remains stable whereas that for LFP does not. This demonstrates the efficient transport capability of Li ions into the nanoscale LFP shell in the core–shell structure of LFP/MCS, which is essential for the improvement of the electrochemical performance.