Investigation of the electrochemical properties and kinetics of a novel SnFe2O4@nitrogen-doped carbon composite anode for lithium-ion batteries

Abstract

Spinel structure transition metal oxides have been developed as promising anode materials for Lithium ion batteries (LIBs). Herein, an inverse spinel SnFe2O4 (SFO) nanoparticles using a simple coprecipitation method, and then a novel SnFe2O4@nitrogen-doped carbon composite (SFO@NC) using poly-dopamine as the carbon source are synthesized, and used as anode materials. SFO@NC delivers high initial charge/discharge capacities of 1140.4/2148.2 mAh g−1 at a current density of 0.2 A g−1, and maintains a high reversible capacity of 1030 mAh g−1 after 300 cycles, also exhibits excellent rate performance with 669.6 mAh g−1 at the current density of 2.0 A g−1. The Li+ storage performance in SFO@NC is far superior to those of pure SFO, which is attributed to the nitrogen doped carbon layer can supply more active sites, enhance the conductivity of the electrode and buffer the volume change of SnFe2O4 during lithium ion in-/deinsertion. Moreover, the Li+ storage kinetics in SFO and SFO@NC have been investigated by measuring cyclic voltammetry (CV) at different scan rates and the electrochemical impedance spectroscopy (EIS) at different temperatures. The results indicate that the Li+ storage behavior of SFO@NC is a combination of capacitive and diffusion-controlled processes, and the barrier energy for the Li+ transport in the SEI film (ΔEa,SEI), the activation energy of the charge transfer in the double layer (ΔEa,CT), and the diffusion activation energy of Li+ in the anode (ΔEa,D) are determined to be 35.05, 52.63 and 58.9 kJ mol−1 with the SFO@NC; and 43.81, 54.75 and 42.6 kJ mol−1 with the pure SFO, respectively. Obviously, the lithium ions are easily intercalated and deintercalated in the SFO@NC anode in kinetics.