3D Binder-Free Mo@CoO Electrodes Directly Manufactured in One Step via Electric Discharge Machining for In-Plane Microsupercapacitor Application.

Cobalt oxide-based in-plane microsupercapacitors (IPMSCs) stand out as a favorable choice for various applications in energy sources for the Internet of Things (IoT) and other microelectronic devices due to their abundant natural resources and high theoretical specific capacitance. However, the low electronic conductivity of cobalt oxide greatly hinders its further application in energy storage devices. Herein, a new manufacturing method of electric discharging machining (EDM), which is simple, safe, efficient, and environment-friendly, has been developed for synthesizing Mo-doped and oxygen-vacancy-enriched Co-CoO (Mo@Co-CoO) integrated microelectrodes for efficiently constructing Mo@Co-CoO IPMSCs with customized structures in a single step for the first time. The Mo@Co-CoO IPMSCs with three loops (IPMSCs3) exhibited a maximum areal capacitance of 30.4 mF cm at 2 mV s. Moreover, the Mo@Co-CoO IPMSCs3 showed good capacitive behavior at a super-high scanning rate of 100 V s, which is around 500-1000 times higher than most reported CoO-based electrodes. It is important to note that the IPMSCs were fabricated using a one-step EDM process without any assistance of other material processing techniques, toxic chemicals, low conductivity binders, exceptional current collectors, and conductive fillers. This novel fabrication method developed in this research opens a new avenue to simplify material synthesis, providing a novel way for realizing intelligent, digital, and green manufacturing of various metal oxide materials, microelectrodes, and microdevices.