Stable 3D porous N-MXene/NiCo2S4 network with Ni–O atomic bridging for printed hybrid micro-supercapacitors

The vision of "Internet of Everything" marked by wearable and multi-functional microelectronics technology has a profound impact on our lives, and the requirements for micro-supercapacitors (MSCs) are also constantly increasing. Compared to traditional capacitors, there is still a lack of systematic investigation on regulating the morphology and internal structure of microelectrodes. Herein, we achieved the inkjet printing of intricate structures, a novel 3D N-MXene/NiCo2S4 porous network, and applied it to long-life hybrid MSCs. A new bridging mechanism of Ni atoms and O atoms is demonstrated by XPS. DFT calculations reveal that the O atoms of N-MXene can capture electrons from Ni atoms of NiCo2S4, resulting in charge redistribution in the interfacial region of 3D N-MXene/NiCo2S4, thereby realizing enhanced structural stability of the composite material. Due to the gradual release of active sites within the porous network, its capacitance retention rate can be as high as 99.1 % after 25,000 charge and discharge tests. With a wide voltage window of 1.6 V, a volumetric capacitance of 983.9 F cm−3, and an energy density of 342.4 mWh cm−3, the MSCs perform better than previously reported inkjet-printed MSCs. Our work demonstrates a new strategy to regulate the surface morphology and internal structure of the microelectrodes by high-precision inkjet printing to improve the performance of the MSCs.