Synthesis‐Driven Enhancement in Energy Storage Performance of Copper Transition Metal Phosphates for Hybrid Battery‐Supercapacitor Systems

The tremendous advancements in science and technology have resulted in the invention of electronic devices that require greater energy storage capabilities. Hybrid supercapacitors (SCs) gain promising interest due to their exceptional electrochemical performance similar to batteries (high‐energy density) and SCs (high‐power density). The excellent performance of the electrode material is significantly influenced by the employed synthesis route. The copper phosphate (Cu 3 (PO 4 ) 2 ) nanomaterials are synthesized using hydrothermal and sonochemical techniques. Two‐ and three‐electrode configurations are utilized to evaluate the electrochemical performance of the as‐prepared nanomaterials. An incredible specific capacity of 443.86 C g −1 at 1.4 A g −1 is achieved through sonochemically obtained nanomaterial (S2). In two‐electrode configuration, S2 is used as a positive electrode material to fabricate an asymmetric device, which provides an energy density of 51.2 Wh kg −1 and power density of 6800 W kg −1 at 0.9 and 8.0 A g −1 , respectively. The device also demonstrates an exceptional capacity retention of 93.45% after 1000 galvanostatic charge–discharge cycles at 5 A g −1 . Overall, the outcomes suggest that the sonochemical method is the most effective approach for the preparation of nanomaterials for next‐generation energy storage applications.