Enhancement of optically chargeable capacity by heterojunction construction via precipitation in Li-doped sodium niobate

Abstract

Due to the depletion of fossil fuels, extensive CO₂ emissions, and growing demand for electrochemical energy, it is important to develop further utilization of renewable energy, as well as advanced energy storage techniques. To this end, the optically chargeable supercapacitor, which can convert the photon energy of solar light into electrochemical energy and store it for long-term usage, attracts extensive investigations. Among these, heterojunction construction was revealed as an effective method to enhance capacity. Recent works have reported the implementations of precipitation in ceramics, where the introduced matrix-precipitate two-phase structure is inspiring for constructing heterojunction, whereas it was seldom reported. In this work, Li-doped NaNbO₃ electrode material was prepared by adopting a multi-step solid reaction to precipitate LiNbO₃ and construct LiNbO₃/NaNbO₃ heterojunctions. The electrochemical measurement demonstrates an enhanced optically chargeable capacity of roughly 85% increase at a scan rate of 1 mV/s and a four-fold increase at a charging–discharging current density of 1 A/g, as well as outstanding stability by introducing precipitates and constructing heterojunctions. This finding proposes a novel methodology design of heterojunction construction via precipitation to enhance the optically chargeable capacity of supercapacitor electrode materials and, therefore, may open up a potentially new application field for precipitate-tuned functionality in functional ceramics.