UC Irvine

Niobium pentoxide, Nb2O5, is a lithium-ion battery anode material that exhibits pseudocapacitance,particularly in the orthorhombic phase, from fast lithium intercalation kinetics. While the electrochemical characteristics of this material have been well studied, there is a gap in the knowledge of long-term cycle stability and degradation analysis of this material. Upon 10,000 lithiation/delithiation cycles, the main degradation pathways observed for electrophoretically deposited thin films of orthorhombic Nb2O5 were amorphization of the orthorhombic structure and delamination of the thin films from the current collector. Additionally, these films boasted exceptional capacities that exceeded the theoretical Faradaic capacity. This phenomenon can be attributed to high non-Faradaic surface capacitance arising from the observed 70% porosity of the films. Since pristine Nb2O5 is very insulating, these pores can only be accessed and contribute significantly to the capacitance if the conductivity of the films changes as a function of lithiation. In situ conductivity measurements of T-Nb2O5 nanoribbons illustrate a large ∼2000-fold increase in conductivity upon lithiation. Study of degradation and conductivity of electrophoretically deposited T- Nb2O5 is crucial in understanding why this material can perform beyond theoretical limits and how the electrochemical performance can be further improved.