A versatile strategy of wire electric discharge machining for one-step fabrication of molybdenum-based micro-supercapacitors: from MoOx to CuMoOx

In recent years, molybdenum-based ceramic materials have emerged as promising candidates in energy storage devices because of their high theoretical charge storage capacitance and natural abundance. However, the low electronic conductivity and complex preparation procedures significantly hinder their further development. Herein, a versatile strategy of wire electric discharge machining (WEDM) was developed for one-step fabrication of molybdenum-based ceramic pseudocapacitive interdigital micro-supercapacitors (PMSCs), including MoOx PMSCs and CuMoOx PMSCs. It was found that PMSCs containing binary metal oxides (BMs) of CuMoOx showed much higher capacitance than that of MoOx PMSCs owing to the synergy of contributions of the individual metal oxides. Moreover, this investigation demonstrates that the machining pulse width of WEDM could directly tailor the capacitive performance of CuMoOx PMSCs. Compared to machining pulse width of 6 μs and 18 μs, the CuMoOx PMSCs fabricated by the machining pulse width of 12 μs (CuMoPMSCs12) showed superior performance. The capacitance of CuMoPMSCs12 was 68 mF cm⁻2 at 5 mV s− 1 and retained at 6.57 mF cm− 2 at extremely high sweep rate of 10 V s− 1. Additionally, an impressive capacitance retention of 100.93% was achieved for the CuMoPMSCs12 micro-device. This WEDM strategy developed in this work showed great potential for single-step preparing various molybdenum-based ceramic materials for PMSCs, micro-batteries and microsensors.