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.