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In Situ EXAFS‐Derived Mechanism of Highly Reversible Tin Phosphide/Graphite Composite Anode for Li‐Ion Batteries
Author(s) -
Ding Yujia,
Li ZheFei,
Timofeeva Elena V.,
Segre Carlo U.
Publication year - 2018
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201702134
Subject(s) - materials science , anode , phosphide , tin , extended x ray absorption fine structure , graphite , chemical engineering , amorphous solid , composite number , absorption (acoustics) , phase (matter) , electrode , metal , absorption spectroscopy , composite material , metallurgy , crystallography , chemistry , organic chemistry , physics , quantum mechanics , engineering
Abstract A novel Sn 4 P 3 /graphite composite anode material with superior capacity and cycling performance (651 mA h g −1 after 100 cycles) is investigated by in situ X‐ray absorption spectroscopy. Extended X‐ray absorption fine structure modeling and detailed analysis of local environment changes are correlated to the cell capacity and reveal the mechanism of lithiation/delithiation process. Results show that in the first two lithiation/delithiation cycles crystalline Sn 4 P 3 is fully converted to an amorphous SnP x phase, which in further cycles participates in reversible conversion and alloying reactions. The superior reversibility of this material is attributed to the highly dispersed SnP x in the graphite matrix, which provides enhanced electrical conductivity and prevents aggregation of Sn clusters during the lithiation/delithiation process. The gradual capacity fading in long‐term cycling is attributed to the observed increase in the size and the amount of metallic Sn clusters in the delithiated state, correlated to the reduced recovery of the SnP x phase. This paper reveals the mechanism responsible for the highly reversible tin phosphides and provides insights for improving the capacity and cycle life of conversion and alloying materials.