Perovskite framework NH4FeF3/carbon composite nanosheets as a potential anode material for Li and Na ion storageElectronic supplementary information (ESI) available: N2 adsorption/desorption isotherm curves of NH4FeF3/CNS. XRD patterns of NH4FeF3/CNS treated with HCl and the different products obtained at different reaction times and different calcination temperatures. TG and DSC curves of NH4FeF3/CNS and FeF2/CNS. XPS spectra of N1s of pristine and first discharged/recharged NH4FeF3/CNS. The ch

• Main Authors: Kong, Minhong, Liu, Kunhong, Ning, Jinyu, Zhou, Jisheng, Song, Huaihe
• Format: Article
• Language: English
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c7ta05466a

Transition metal fluorides (TMFs) have received increasing attention as promising electrode materials for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) due to their resource abundance, low-cost and high specific capacities. However, TMFs usually suffer from low electron conductivity and high Li/Na ion diffusion resistance, which lead to rapid capacity fading. In order to further improve their electrochemical performance, designs of carbon-based TMFs with crystal topologies favorable for Li/Na ion diffusion are greatly needed. Here, NH 4 FeF 3 /carbon nanosheet (NH 4 FeF 3 /CNS) composites were prepared via a facile co-pyrolysis of ferric acetylacetonate and NH 4 F. NH 4 FeF 3 has an open framework structure with a perovskite topology, in which FeF 6 octahedral monomers are connected with each other via F − anions to form cavities, and NH 4 + cations reside inside the cavities. The interesting perovskite structure is favorable for Li/Na ion storage. When used as an anode for LIBs, the NH 4 FeF 3 /CNS exhibits a specific capacity of 1000 mA h g −1 at 200 mA g −1 after 300 cycles, which is much higher than those of other reported TMFs. When used as an anode for SIBs, the NH 4 FeF 3 /CNS also exhibits a high specific capacity of 504 mA h g −1 as well as better rate-performance and cycling stability. The better electrochemical performance of NH 4 FeF 3 /CNS composites for both LIBs and SIBs should be ascribed to, on one hand, the fact that the perovskite framework structure of NH 4 FeF 3 with NH 4 + fillers has kinetically favorable Li/Na ion channels so as to be helpful to alleviate volume expansion during the cycling process and, on the other hand, the fact that carbon nanosheets can act as a conductive network to improve the conductivity of NH 4 FeF 3 nanoparticles. Perovskite framework NH 4 FeF 3 /CNS composites were prepared by an in situ co-pyrolysis method and exhibit better performance as anodes for both LIBs and SIBs.