K1−xMn1+x/2[Fe(CN)6]·yH2O Prussian blue analogues as an anode material for lithium-ion batteries

Abstract

Hexacyanoferrate, KMn[Fe(CN)6]·yH2O (KMnHCF), a Prussian blue analogue (PBA), is synthesized by a solution precipitation method under alkaline condition at room temperature. After treated with diluted hydrochloride acid, the KMnHCF is turned into Mn3[Fe(CN)6]2·yH2O (MnHCF). Then both synthesized KMnHCF and MnHCF are applied as anode material for lithium ion batteries (LIBs). The KMnHCF anode exhibits a super electrochemical performance than MnHCF. It shows a very low discharge voltage plateau of 0.6 V, an initial capacity of 777 mAh g−1, and a reversible capacity of 434 mAh g−1 after 50 cycles at a current density of 50 mA g−1. Furthermore, it keeps 425 mAh g−1 after 100 cycles at 100 mA g−1 and 215 mAh g−1 after 200 cycles even at 500 mA g−1. It is remarkable that the coulombic efficiency can be maintained larger than 98.4% from the 5th cycle at 50 mA g−1, 99.2% at 100 mA g−1, and 96.8% even at 500 mA g−1. In addition, the original structure of the KMnHCF has no obvious change after lithiation/de-lithiation based on the ex-situ X-ray powder diffraction (XRD) and Fourier transform infrared spectrometer (FT-IR) characterization, indicating large channels and interstitial sites in the open-framework can allow rapid insertion and extraction of Li+ and constrain volume expansion during charge/discharge process.