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Br‐Doped Li 4 Ti 5 O 12 and Composite TiO 2 Anodes for Li‐ion Batteries: Synchrotron X‐Ray and in situ Neutron Diffraction Studies
Author(s) -
Du Guodong,
Sharma Neeraj,
Peterson Vanessa K.,
Kimpton Justin A.,
Jia Dianzeng,
Guo Zaiping
Publication year - 2011
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201100846
Subject(s) - materials science , anatase , rietveld refinement , neutron diffraction , analytical chemistry (journal) , rutile , electrochemistry , phase (matter) , anode , crystal structure , composite number , x ray crystallography , electrode , diffraction , crystallography , chemical engineering , chemistry , composite material , optics , catalysis , biochemistry , physics , organic chemistry , chromatography , photocatalysis , engineering
Synchrotron X‐ray diffraction data were used to determine the phase purity and re‐evaluate the crystal‐structure of Li 4 Ti 5 O 12‐ x Br x electrode materials (where the synthetic chemical inputs are x = 0.05, 0.10 0.20, 0.30). A maximum of x ′ = 0.12 Br, where x ′ is the Rietveld‐refined value, can be substituted into the crystal structure with at least 2% rutile TiO 2 forming as a second phase. Higher Br concentrations induced the formation of a third, presumably Br‐rich, phase. These materials function as composite anodes that contain mixtures of TiO 2 , Li 4 Ti 5 O 12‐ x Br x , and a Br‐rich third, unknown, phase. The minor quantities of the secondary phases in combination with Li 4 Ti 5 O 12‐ x Br x where x ′ ∼ 0.1 were found to correspond to the optimum in electrochemical properties, while larger quantities of the secondary phases contributed to the degradation of the performance. In situ neutron diffraction of a composite anatase TiO 2 /Li 4 Ti 5 O 12 anode within a custom‐built battery was used to determine the electrochemical function of the TiO 2 component. The Li 4 Ti 5 O 12 component was found to be electrochemically active at lower voltages (1.5 V) relative to TiO 2 (1.7 V). This enabled Li insertion/extraction to be tuned through the choice of voltage range in both components of this composite or in the anatase TiO 2 phase only. The use of composite materials may facilitate the development of multi‐component electrodes where different active materials can be cycled in order to tune power output.