Directionally assembled FeCO3 nanoparticles wrapped with rGO enabled by the synergy of tartaric and ascorbic acids for lithium/sodium storage

Abstract

Ferrous carbonate (FeCO3) particles synthesized by conventional routes generally possess large-size bulk structures with the drawbacks of low conductivity and easy pulverization, thereby limiting their promising application as high-capacity anodes for lithium/sodium ion batteries (LIBs/SIBs). Herein, a robust strategy via the synergy of tartaric and ascorbic acids (TA/AA) is developed to craft FeCO3 dumbbells that are directionally assembled by ultrafine nanoparticles and uniformly encapsulated in reduced graphene oxide matrixes (denoted FeCO3 NADs-rGO). It is noteworthy that TA serves as a capping agent to inhibit the overgrowth of FeCO3 nanoparticles and guide their directional assembly into dumbbells. Concurrently, AA functions as a reductant to prevent the oxidation of Fe2+ and initiate the reduction of GO. Remarkably, benefiting from the efficient synergy of hierarchical architecture and rGO encapsulation, FeCO3 NADs-rGO delivers highly-reversible lithium and sodium storage capacities of 1853 and 641 mAh/g in the 1200th and 100th cycles at 100 and 20 mA g−1, respectively, which are 2.1 and 3.9-fold over FeCO3 micron peanut kernels-rGO (884 and 163 mAh/g) fabricated without introducing TA. As revealed by experimental investigations and theoretical calculations, FeCO3 nanoparticles shorten the ion transfer distance and rGO accelerates the electron conduction to boost the electrochemical kinetics for high-rate capability. More importantly, the ample mesopores of FeCO3 NADs accommodate the inward stress and the rGO buffer the outward expansion of lithiated/sodiated FeCO3 NADs to strengthen the electrode durability. As such, FeCO3 NADs-rGO may stand out as a superior LIB/SIB anode, and the implementation of facile capping and reductant co-regulators (e.g., TA and AA) could synergistically render the creation of various rGO-based nanocomposites with outstanding mechanical flexibility and electrochemical activity for advanced energy storage.