Scalable Synthesis of Ni<sub>3</sub>B<sub>2</sub>O<sub>6</sub> Nanograins and Fabrication of a Coin Cell Supercapacitor for Powering Temperature Sensor Devices
Beena Somanath, C. Manjunatha, Yash Athreya, Shwetha KP, Nelsa Abraham, Suresh Babu Viswanathan, Sudha Kamath MK, S. Girish Kumar, Ajit Khosla
Abstract
In this work, we present a facile and scalable method to synthesize nickel orthoborate nanograins (NBNG) by a simple solution combustion method. The expected crystallinity, phases, and functional groups of NBNG were confirmed by X-ray diffraction (XRD), Raman, and Fourier transform infrared (FTIR) spectroscopy techniques. In addition, the morphological features, chemical composition, and surface area of the NBNG nanograins were analyzed by field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller (BET) techniques. Electrochemical studies confirm that the NBNG displayed a specific capacitance of 684 F g –1 at 1 A g –1 with a retention of 73.6% after 5000 cycles, which is found to be a very promising value compared to the data reported so far. Further, its asymmetric coin cells prepared by using activated carbon (AC) as the opposite electrode (NBNG//AC) displayed a very encouraging specific capacitance of 138.86 F g –1 at 1 A g –1 (with a retention of 83% after 5000 cycles), an energy density of 59.06 Wh kg –1, and a power density of 1166.67 W kg –1 . Inspired by these values, we further used an NBNG//AC supercapacitor device to power the Arduino microcontroller circuit-based temperature sensor device. The sensor device powered by four NBNG//AC coin cells showed the desired temperatures to be between 25 and 34 °C. The electrochemical results of NBNG//AC reported in this work will surely inspire many material scientists to further explore and develop highly functional transition metal borate-based materials for energy and electronic device applications.