Carbon coated tetrakaidecahedron tin ferrite (SnFe2O4) with high pseudocapacitance as anode material for lithium-ion batteries

Abstract

A series of carbon coated SnFe2O4 (SFO) with octahedron, decahedron and tetrakaidecahedron morphologies have been synthesized by a simple hydrothermal process using ferrocene as common source of iron and carbon, applying a cationic surfactant CTAB to modify the morphology. Compared with the octahedral SFO (no CTAB) and decahedral SFO-0.1 (with CTAB at the first critical micelle concentration (CMC)), the tetrakaidecahedral SFO-0.7 (with CTAB at the second CMC) as an anode of LIB shows a high charge/discharge capacity of 481.0/482.7 mAh g−1 after 1000 cycles at 2 A g−1,and 281.0/281.6 mAh g−1 after 2000 cycles at 6 A g−1. The investigations on Li-ions inter-/de-intercalation kinetics show that the main rate-controlled step of SFO-0.7 is pseudocapacitive behavior, with higher contribution of 95.88% at a scan rate of 2.0 mV s−1. The results suggest that the carbon layer obtained directly from ferrocene can effectively inhibit the volume expansion and structure damage of SnFe2O4. At the same time, more oxygen-vacancies increase the conductivity, the enhanced strength of the dominant (111) plane can adsorb Li-ions more easily, and the smaller SnFe2O4 can reduce the diffusion distance of Li-ions, all of which lead to a high and stable Li-ions storage capacity and rate capability.