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Ternary metal fluorides as high-energy cathodes with low cycling hysteresis.

Nature communications (2015-03-27)
Feng Wang, Sung-Wook Kim, Dong-Hwa Seo, Kisuk Kang, Liping Wang, Dong Su, John J Vajo, John Wang, Jason Graetz
ABSTRACT

Transition metal fluorides are an appealing alternative to conventional intercalation compounds for use as cathodes in next-generation lithium batteries due to their extremely high capacity (3-4 times greater than the current state-of-the-art). However, issues related to reversibility, energy efficiency and kinetics prevent their practical application. Here we report on the synthesis, structural and electrochemical properties of ternary metal fluorides (M(1)yM(2)(1-y)F(x): M(1), M(2) = Fe, Cu), which may overcome these issues. By substituting Cu into the Fe lattice, forming the solid-solution Cu(y)Fe(1-y)F(2), reversible Cu and Fe redox reactions are achieved with surprisingly small hysteresis (<150 mV). This finding indicates that cation substitution may provide a new avenue for tailoring key electrochemical properties of conversion electrodes. Although the reversible capacity of Cu conversion fades rapidly, likely due to Cu(+) dissolution, the low hysteresis and high energy suggest that a Cu-based fluoride cathode remains an intriguing candidate for rechargeable lithium batteries.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
1-Methyl-2-pyrrolidinone, anhydrous, 99.5%
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1-Methyl-2-pyrrolidinone, ACS reagent, ≥99.0%
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1-Methyl-2-pyrrolidinone, ReagentPlus®, 99%
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1-Methyl-2-pyrrolidinone, suitable for HPLC, ≥99%
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1-Methyl-2-pyrrolidinone, analytical standard