A new dual-ion battery based on amorphous carbon

The Na-based dual-ion batteries (NDIBs), combining the advantages of Na-ion batteries and dual-ion batteries, are attracting more attention due to their merits of abundant source, low cost and high energy density. However, the main challenges faced by NDIBs are their low capacity and poor cycling. Herein, we report a new ion storage mechanism for high-performance NDIBs using amorphous carbon (AOMC) as cathode. Unlike the graphite carbon that can only accommodate the PF6- anion (typical DIB system), the AOMC herein can both accommodate Na+ cation and PF6- anion due to its amorphous feature, which is conceptually new dual-ion system for achieving much higher capacity. Ex-situ X-ray photoelectron spectroscopy, X-ray diffraction and Raman studies reveal that the disordered carbon in the AOMC can be transformed to the partial graphitic stacking in short range, improving both capacity and cycling stability of NDIBs. As a consequence, the AOMC delivers a highly reversible storage capacity of 136 mAh g-1 for 800 cycles at a very high current density of 2.0 A g-1, much higher than all the reported NDIBs. Such concept can be generalized to develop high-performance dual-ion full cell using sodium ion pre-intercalated materials as anode and AOMC as cathode.