Li⁺Insertion/Extraction Properties for TiNb₂O₇Single Particle Characterized by a Particle-Current Collector Integrated Microelectrode

Abstract

In this study, we evaluate the electrochemical properties of TiNb 2 O 7 (TNO) single particle using a particle-current collector integrated microelectrode, in which TNO single particle with the size of approximately 10 m was bonded on the tip of a tungsten microelectrode by platinum deposition using a focused ion beam process unit (FIB). Cyclic voltammogram of TNO single particle showed the reversible redox peaks at around 1.6-1.7 V vs. Li/Li + . Anodic peak current is higher than cathodic one at a fixed scan rate, indicating faster reaction during Li + extraction (i.e. discharge) than Li + insertion (i.e. charge) of TNO particle. This tendency was also confirmed in C-rate dependence of charge and discharge capacities. From the results for galvanostatic intermittent titration testing (GITT), we confirmed that at the equilibrium potential vs. Li/Li + below 1.5 V, apparent chemical diffusion coefficient of Li + in TNO at Li + extraction process is much larger than at Li + insertion process. Furthermore, the capacity retention of TNO single particle tested at current of 10C after 2000 cycles was above 99%, indicating excellent intrinsic stability of TNO single particle for Li + insertion and extraction reaction.