Microsized, spherical, three-dimensional (3D) graphene-based composites as electrode materials exhibit improved tap density and electrochemical properties. In this study, we report 3D LiMn0.75Fe0.25PO4/reduced graphene oxide microspheres synthesized by one-step salt-assisted spray drying using a mixed solution containing a precursor salt and graphene oxide and a subsequent heat treatment. During this process, it was found that the type of metal salt used has significant effects on the morphology, phase purity, and electrochemical properties of the synthesized samples. Furthermore, the amount of the chelating agent used also affects the phase purity and electrochemical properties of the samples. The composite exhibited a high tap density (1.1 g cm-3) as well as a gravimetric capacity of 161 mA h-1 and volumetric capacity of 281 mA h cm-3 at 0.05 C-rate. It also exhibited excellent rate capability, delivering a discharge capacity of 90 mA h-1 at 60 C-rate. Furthermore, the microspheres exhibited high energy efficiency and good cyclability, showing a capacity retention rate of 93% after 1000 cycles at 10 C-rate.
Bibliographical noteFunding Information:
This work was supported by the energy efficiency and resources grant (No: 20122010100140) of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) funded by the Ministry of Knowledge Economy, Korean government. This work was also supported by POSCO and Business for Cooperative R and D between Industry, Academy, and Research Institute funded Korea Small and Medium Business Administration in 2015 (grant no. C0300716). This research was also supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning (2015R1A2A2A03006633).
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