Ammonia‐Annealed TiO2 as a Negative Electrode Material in Li‐Ion Batteries: N Doping or Oxygen Deficiency?

Improving the chemical diffusion of Li ions in anatase TiO₂ is essential to enhance its rate capability as a negative electrode for Li‐ion batteries. Ammonia annealing has been used to improve the rate capability of Li₄Ti₅O₁₂. Similarly, ammonia annealing improves the Li‐ion storage performance of anatase TiO₂ in terms of the stability upon cycling and the C‐rate capability. In order to distinguish whether N doping or oxygen deficiencies, both introduced upon ammonia annealing, are more relevant for the observed improvement, a systematic electrochemical study was performed. The results suggest that the creation of oxygen vacancies upon ammonia annealing is the main reason for the improvement of the stability and C‐rate capability.     

Magneto-structural defects on a congested nanoscopic polyradical dendrimer

The new polychlorotriphenylmethyl tetraradical 1 has been obtained and its magnetic properties studied. The large overcrowding present in this dendritic radical has been shown not only to affect its synthesis but its magnetic properties. Even though steric hindrance is an extremely efficient tool to increase the persistence of high-spin species, it may lead to undesired steric congestions that disfavor the desired ferromagnetic coupling between meta connected radical units.     

Fast Li-ion Storage and Dynamics in TiO2 Nanoparticle Clusters Probed by Smart Scanning Electrochemical Cell Microscopy

Anatase TiO₂ is a promising material for Li-ion (Li⁺) batteries with fast charging capability. However, Li⁺ (de)intercalation dynamics in TiO₂ 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 TiO₂ nanoparticle clusters. Directly probing active nanoparticles revealed that TiO₂ 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 TiO₂ 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.