Vacancy-modified few-layered GaN crystal for novel high-temperature energy storage

Abstract

Exploring energy storage materials with ultralong cycle lifespan and high energy/power density in extremely high-temperature environments is crucial. In this work, a gallium nitride (GaN) crystal is applied in a high-temperature energy storage field for the first time, and the relevant reasons for the improved energy storage are proposed. A few-layered GaN crystal rich in N-vacancies is designed and fabricated via an efficient and facile strategy, which further increases its specific area and active sites. An ionic-liquid-based supercapacitor device is developed by combining the GaN and ionic liquids. This device exhibits high specific capacity (52.58 mF cm⁻² at 0.8 mA cm⁻²) and a wide voltage window (0–2.7 V). Even at a high temperature of 150 °C and a scan rate of up to 50 V s⁻¹, 86.2% capacity is retained at 8 mA cm⁻² over 10 000 cycles. Additionally, the energy storage mechanism of GaN with N vacancies is further investigated using density functional theory calculations. This study systematically demonstrates the application potential of GaN crystals in the field of high-temperature energy storage, and provides a strategy for the application of wide-bandgap semiconductors in a new field.