Improving rate performance of FeC2O4/rGO composites on lithium storage via single-polymerization‐induced electrostatic self‐assembly

Abstract

Based on the wide interlayer distance for ions diffusion, iron (II) oxalate exhibits excellent lithium storage ability. However, the local deposition of metallic nanoparticles of Fe⁰ leads to low electrochemical reactivity, which hinders the actual application of FeC₂O₄ in large current regions (>5C). To solve this problem, a strong cationic polymeric electrolyte, polyelectrolyte diallyl dimethyl ammonium (PDDA), was introduced to construct a [FeC₂O₄(PDDA)]⁺ ligand. By single-polymerization‐induced electrostatic self-assembly, the [FeC₂O₄(PDDA)]⁺ ligand was combined with the surface-charged rGO to produce a FeC₂O₄/rGO material. It is proved that the rGO carrier improves the interparticle conductivity, electrochemical activity and structure stability of the iron (II) oxalate particles, ensuring the stability of Li || FeC₂O₄/rGO battery at a rapid charging rate of 20C (8 A g⁻¹) for more than 500 cycles (with the special capacity of 713 mAh g⁻¹). Compared with FeC₂O₄ electrode, owning to high reactivity of rGO and continuously activating on the nanoscale Fe metal generated at ∼0.75 V, FeC₂O₄/rGO shows higher electrochemical activity of conversion reaction in the first 50 cycles and better reversibility in the rate charge–discharge test (the capacity rapidly increased to 1158.8 mAh g⁻¹ after 20C cycles). This work reveals how the structural design of conducting and supporting the carrier can achieve fast charging for iron (II) oxalate lithium-ion batteries.