Conjugately configured supercapacitors: Mitigating self-discharge based on pairs of pre-lithiated niobium oxides

Abstract

Self-discharge has attracted extensive attention as one of the main reasons limiting the wider application of supercapacitors. Current strategies for suppressing self-discharge are mainly focused on modifying the properties of each component. However, the effectiveness is limited by the lack of consideration for device configuration to maximize the potential of the materials. Herein, we report a novel conjugately configured supercapacitor by coupling pairs of pre-lithiated niobium oxide with the unique working mechanism of intercalation pseudocapacitance. The symmetric supercapacitor using conjugated LixNb2O5 vs. Li2-xNb2O5 retains 40% voltage in 50 h during aging. When kept at 1.0 V for 24 h, a low leakage current of 1.5 μA is observed, which has obviously improved stability compared to conventional AC vs. AC symmetric supercapacitor (10.7 times higher voltage retention rate, 0.5 times lower leakage current). The improved stability endowed by the conjugated configuration is evidenced by the comparable stability of both niobium oxide and AC when lithium metal is used as the counter electrode. The successful suppressing of self-discharge based on the device-level conjugated configuration is expected to serve as a general strategy for various types symmetric supercapacitors.