For large storage batteries, cost performance is more important than energy density. Iron-based conversion-type cathode active materials are promising because this material group satisfies both low-cost and high-capacity requirements. In particular, iron fluoride is notable for its relatively high discharge voltage. However, the electronic conductivity of FeF3 is poor and it has large discharge-charge overvoltage. To solve these issues, xFeF3-V2O5/C (9xFeF3-9V2O5–P2O5) was investigated and the composition with x = 2 was shown to be optimal. Furthermore, the cyclability of 2FeF3–V2O5/C was improved by changing the salt from LiPF6 to LiClO4 and changing the solvent from DMC to EMC. Although the V2O5 glass component showed irreversible capacity due to Li trapping in the glass matrix at the first cycle, the irreversible capacity at the first cycle was successfully compensated by the addition of LiF as a sacrificial salt.
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