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Superstructure in the Metastable Intermediate‐Phase Li 2/3 FePO 4 Accelerating the Lithium Battery Cathode Reaction
Author(s) -
Nishimura Shinichi,
Natsui Ryuichi,
Yamada Atsuo
Publication year - 2015
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201501165
Subject(s) - electrochemistry , metastability , superstructure , eutectic system , materials science , ion , cathode , lithium (medication) , valence (chemistry) , polaron , crystallization , chemical physics , chemistry , electrode , electron , alloy , thermodynamics , medicine , physics , organic chemistry , quantum mechanics , composite material , endocrinology
LiFePO 4 is an important cathode material for lithium‐ion batteries. Regardless of the biphasic reaction between the insulating end members, Li x FePO 4 , x ≈0 and x ≈1, optimization of the nanostructured architecture has substantially improved the power density of positive LiFePO 4 electrode. The charge transport that occurs in the interphase region across the biphasic boundary is the primary stage of solid‐state electrochemical reactions in which the Li concentrations and the valence state of Fe deviate significantly from the equilibrium end members. Complex interactions among Li ions and charges at the Fe sites have made understanding stability and transport properties of the intermediate domains difficult. Long‐range ordering at metastable intermediate eutectic composition of Li 2/3 FePO 4 has now been discovered and its superstructure determined, which reflected predominant polaron crystallization at the Fe sites followed by Li + redistribution to optimize the LiFe interactions.