Fast Li-ion Storage and Dynamics in TiO 2 Nanoparticle Clusters Probed by Smart Scanning Electrochemical Cell Microscopy.

Anatase TiO is a promising material for Li-ion (Li ) batteries with fast charging capability. However, Li (de)intercalation dynamics in TiO remain elusive and reported diffusivities span many orders of magnitude. Here, we develop a smart protocol for scanning electrochemical cell microscopy (SECCM) with in situ optical microscopy (OM) to enable the high-throughput charge/discharge analysis of single TiO nanoparticle clusters. Directly probing active nanoparticles revealed that TiO with a size of ≈50 nm can store over 30 % of the theoretical capacity at an extremely fast charge/discharge rate of ≈100 C. This finding of fast Li storage in TiO particles strengthens its potential for fast-charging batteries. More generally, smart SECCM-OM should find wide applications for high-throughput electrochemical screening of nanostructured materials.