Graphite carbon-encapsulated metal nanoparticles derived from Prussian blue analogs growing on natural loofa as cathode materials for rechargeable aluminum-ion batteries

Kaiqiang Zhang,Mehdi Ostadhassan,Bailey Bubach,Ho Won Jang,Mohammadreza Shokouhimehr,Ji-Won Choi,Tae Hyung Lee

doi:10.1038/s41598-019-50154-8

Abstract

Aluminum-ion batteries (AIBs) are attracting increasing attention as a potential energy storage system owing to the abundance of Al sources and high charge density of Al3+. However, suitable cathode materials to further advance high-performing AIBs are unavailable. Therefore, we demonstrated the compatibility of elemental metal nanoparticles (NPs) as cathode materials for AIBs. Three types of metal NPs (Co@C, Fe@C, CoFe@C) were formed by in-situ growing Prussian blue analogs (PBAs, Co[Co(CN)6], Fe[Fe(CN)6] and Co[Fe(CN)6]) on a natural loofa (L) by a room-temperature wet chemical method in aqueous bath, followed by a carbonization process. The employed L effectively formed graphite C-encapsulated metal NPs after heat treatment. The discharge capacity of CoFe@C was superior (372 mAh g−1) than others (103 mAh g−1 for Co@C and 75 mAh g−1 for Fe@C). The novel design results in CoFe@C with an outstanding long-term charge/discharge cycling performance (over 1,000 cycles) with a Coulombic efficiency of 94.1%. Ex-situ X-ray diffraction study indicates these metal NP capacities are achieved through a solid-state diffusion-limited Al storage process. This novel design for cathode materials is highly significant for the further development of advanced AIBs in the future.

Highlights

With the gradual reduction of fossil energy resources, increasing environmental problems, and increasing demand for energy, the search for an ideal energy has become highly challenging[1]
We verified the electrochemical activity of elemental metal NPs as cathode materials for aluminum ion batteries (AIBs)
The metal NPs were formed by in-situ grown Prussian blue analogues (PBAs) (CoHCCo, FeHCFe, and CoHCFe) on natural and low-cost L surface, followed by carbonization

Summary

Introduction

With the gradual reduction of fossil energy resources, increasing environmental problems, and increasing demand for energy, the search for an ideal energy has become highly challenging[1]. Integrating clean, sustainable energy resources (solar, wind, geothermal, etc.) into the electric grid is considered as a potential solution[2] Their intermittencies are major obstacles that require energy storage devices. Www.nature.com/scientificreports on aluminum-ion batteries has increased in the last five years, primarily focusing on the development of cathode materials to overcome the higher charge density of Al3+ or large ionic radius of AlCl4− 9. Carbon species are expected to crystallize spontaneously on the surface of metal NPs at a relatively low temperature to, in situ, form a graphite C layer for the protection of the metal NPs. The remaining effort is to obtain a suitable process and material to grow the precursor of the metal NPs on the L surface. Among the MOFs, Prussian blue analogues (PBAs) exhibit the advantage of rich-C, simple synthesis, and easy mass production at room temperature by a facile wet chemistry method in aqueous base[19,20]

Methods

Results

Conclusion