Boosting the lithium-ion and sodium-ion storage performances of pyrite by regulating the energy barrier of ion transport

Abstract

Pyrite (FeS₂) is a functional material of great importance for lithium/sodium ion batteries (LIBs/SIBs), but its sluggish dynamics greatly hinder its high performance. Here, we demonstrate an effective strategy of regulating the energy barrier of ion transport to significantly enhance the sluggish dynamics of FeS₂ by Co doping. Compared to pristine FeS₂, a series of Co-doped FeS₂ shows enhanced alkali metal ion storage performance and most typically, the optimized Fe_0.7Co_0.3S₂ sample displays high reversible capacities, of 1170 mA h g⁻¹ for LIBs and 650 mA h g⁻¹ for SIBs at a current density of 0.1 A g⁻¹ as well as super long-life cycling stability for SIBs (1200 cycles at 5 A g⁻¹). The evidently enhanced performances of Fe_0.7Co_0.3S₂ for LIBs/SIBs can be attributed to its significantly decreased activation energy of ion transport, thus leading to greatly accelerated ion transport dynamics. Furthermore, galvanostatic intermittent titration technique (GITT) experiments also support this important regulation effect of Co doping on the ion transport dynamics of FeS₂. The excellent ion transport dynamics induce a strong pseudo-capacitance behavior in both SIBs and LIBs, and their pseudo-capacitance contributions are more than 90% at 1.0 mV s⁻¹. This work provides a new perspective to improve the alkali metal ion storage performance by optimizing the ion transport dynamics.