Deterministic Effect of the Solid-State Diffusion Energy Barrier for a Charge Carrier on the Self-Discharge of Supercapacitors

The further development of fast electrochemical devices is hindered by self-discharge. Current strategies for suppressing self-discharge are mainly focused on the extrinsic and general mechanisms, including Faradaic reactions, charge redistribution, and Ohmic leakage. However, the self-discharge process is still severe for conventional supercapacitors. Herein, we unravel the deterministic effect of a solid-state diffusion energy barrier by constructing conjugately configured supercapacitors based on pairs of prelithiated niobium oxides with similar intercalation pseudocapacitive processes but different phases. This device works with a single type of charge carrier, while materials with various diffusion barriers can be implanted, thus serving as an ideal platform to illustrate the influence of diffusion barrier. The results show that the comprehensive effect of the solid-state diffusion barrier and extrinsic effects drives the self-discharge process. It is worth noting that the diffusion barrier presents an exponential form, which governs the self-discharge of supercapacitors. This work provides a general guidance for suppressing self-discharge for supercapacitors.