(Invited) 3- D Printed Electrode Materials for Low-Cost, Flexible, and Stretchable Energy Storage Devices

The additive manufacturing or 3- D printing technology has recently gained much attention in the industry and academia due to its ability to rapidly produce shape and size versatile 3-D patterns.[1-3] This technology has emerged as a smart manufacturing tool to develop flexible and miniaturized energy storage devices.[4-8] Here we report 3-D printed supercapacitors on the variety of flexible and stretchable substrates including Polydimethylsiloxane (PDMS), Polyurethane and Ecoflex. The supercapacitor electrodes in the planar configuration with 3- D architecture were printed over the substrates. The rGO- Silver nanoparticle ink was used to develop the conducting layer, CNT- MnO 2 ink as a positive electrode, rGO- CNT ink as a negative electrode, and a gel electrolyte ink to form the full device. All the inks were successfully prepared in the water solution without using any additive or binders. The rheological properties of all inks were carefully controlled to achieve good print quality. The developed device exhibits good electrochemical performance within a voltage range of 0 to 2 V. The device displays high areal capacitance of 4.42 F/cm 2 (1146 F/g) at a current density of 2 mA/cm 2 , excellent cycle life (93 % capacitance retention after 10,000 charge-discharge cycles), high energy density, and high power density. Mechanical deformation test of the devices exhibits that linear stretching upto 100 % and radial deformation upto 170 % have a negligible effect on the electrochemical performance of the devices. Therefore, the printed devices are highly flexible and stretchable. The other devices with different shape, size, and thickness were also successfully developed which shows the high scalability of the 3- D printing method. These devices were mounted on complex shaped surfaces and integrated with other electronic devices. The developed devices worked well in all the conditions. Therefore, 3- D printing technology can greatly promote the further development of advanced energy storage devices and other electronics. References: Tian, X., et al., Emerging 3D ‐ printed electrochemical energy storage devices: a critical review. Advanced Energy Materials, 2017. 7 (17): p. 1700127. Sundriyal, P. and S. Bhattacharya, Inkjet-Printed Sensors on Flexible Substrates , in Environmental, Chemical and Medical Sensors . 2018, Springer. p. 89-113. Zhu, C., et al., 3D printed functional nanomaterials for electrochemical energy storage. Nano Today, 2017. 15 : p. 107-120. Sundriyal, P. and S. Bhattacharya, Inkjet-Printed Electrodes on A4 Paper Substrates for Low-Cost, Disposable, and Flexible Asymmetric Supercapacitors. ACS Applied Materials & Interfaces, 2017. 9 (44): p. 38507-38521. Sundriyal, P. and S. Bhattacharya, Scalable Micro-fabrication of Flexible, Solid-state, Inexpensive and High-Performance Planar Micro-supercapacitors through Inkjet Printing Method. ACS Applied Energy Materials, 2019. Sundriyal, P., et al., Recent Advancement in the Fabrication of Energy Storage Devices for Miniaturized Electronics , in Nano-Energetic Materials . 2019, Springer. p. 215-240. Li, H. and J. Liang, Recent Development of Printed Micro ‐ Supercapacitors: Printable Materials, Printing Technologies, and Perspectives. Advanced Materials, 2019: p. 1805864. Sundriyal, P., & Bhattacharya, S. (2019, May). Electrochemical Analysis of the Printed NiCo2O4//Reduced Graphene Oxide Solid-State Hybrid Supercapacitors on Fabric Substrates for Wearable Applications. In Meeting Abstracts (No. 1, pp. 81-81). The Electrochemical Society.