One-step in-situ synthesis of bimetallic-doped disordered carbons as anode for high-performance sodium-ion batteries

Since sodium-ion batteries are considered to be the promising energy storage devices, carbon materials as the anodes have been intensively studied. They have good cycling stability, but their capacities are generally not high enough to meet the increasing demands. In order to solve this problem, a carbon-bimetallic composite is synthesized in one step using a simple pyrolysis method with low-cost biomass and cobalt ferrate as the precursors. This simple synthesis method allows the in-situ production of bi-alloys embedded into disordered carbon matrix derived from the tapioca starch to form high-performance anode material for sodium-ion batteries. The initial discharge capacity is 712 mA h g−1 at 0.05 A g−1and the initial Coulombic efficiency is 89.2%. Moreover, the introduction of bi-alloys not only facilitates the reaction kinetics, but also effectively mitigates the volume expansion and consequently promotes the cyclability. As a result, the half-cell sodium-ion battery delivers a capacity of more than 419 mA h g−1 at a high current of 10 A g−1, and after 200 cycles at a current density of 1 A g−1, its capacity degradation is only 0.2% per cycle with a Coulombic efficiency of about 100%. This high-performance materials with a low-cost preparation method could be great potential for commercialized applications.