Amorphous phase induced high phosphorous-doping in dandelion-like cobalt sulfides for enhanced battery-supercapacitor hybrid device

Phosphorus (P) doping is considered to be an effective method for regulating the physicochemical properties of transition metal sulfides (TMSs) through triggering lattice distortion, improving electronic conductivity, and providing additional active sites for charge storage. However, the large P atom makes it difficult to be incorporated in TMSs, particularly at high doping level. Herein, we develop an amorphous phase induced strategy for efficient P doping in dandelion-like cobalt sulfides, reaching a high concentration of 18 at%. The obtained P-CoS_1.097-6 displays remarkable specific capacity of 536 C g⁻¹ and 502 C g⁻¹ at the current density of 5 A g⁻¹ and 20 A g⁻¹, respectively, due to the enhanced electrical conductivity and rapid ion diffusion. This performance is higher than that of P-CoS_1.097-48 with a low doping level of 7 at% (400 C g⁻¹), the primeval Co_1−xS-6 (345 C g⁻¹), and CoS_1.097-48 (335 C g⁻¹). Based on P-CoS_1.097-6 and activated carbon, the battery-supercapacitor hybrid (BSH) device delivers an electrochemical performance of 22 Wh kg⁻¹ (energy density) and good stability with 88% capacity retained over 6000 cycles.