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

Abstract

Anatase TiO 2 is a promising material for Liion (Li + ) batteries with fast charging capability. However, Li + (de)intercalation dynamics in TiO 2 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 highthroughput charge/discharge analysis of single TiO 2 nanoparticle clusters. Directly probing active nanoparticles revealed that TiO 2 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 2 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.

Link between anisotropic electrochemistry and surface transformations at single‐crystal silicon electrodes: Implications for lithium‐ion batteries

“…Although we applied a voltammetric scan rate that was several orders of magnitude larger than typically used to study electrochemistry at Si electrodes under LiB conditions, the voltammetric responses, particularly for Si(1 0 0) and Si(1 1 0), were similar to those obtained routinely with more conventional electrochemical experiments at slower scan rates, 5,24 but with some new phenomena observed. These studies add to a growing literature that demonstrates the benefits of employing SECCM at relatively fast scan rates for the investigation of battery electrode materials, 34,35,38,39 facilitated by the relative immunity of SECCM to ohmic effects compared to equivalent macroscopic measurements, 40,41 in part as a consequence of the conical tip geometry and the low overall current magnitudes.…”

Measuring the Pseudocapacitive Behavior of Individual V2O5 Particles by Scanning Electrochemical Cell Microscopy

“…This heterogenous electrochemical response in isolated energy storage material particles has been reported by many other groups. 29,31,32,35 In comparisons of the electrochemical properties (redox peaks potential and current, total charge, peak-to-peak separation, and oxidation to reduction charge ratio, details in Figure S7 and Table S1), particle 5 shows fast kinetics and a high oxidation to reduction charge ratio (97.74%), making it the ideal morphology and stability. Meanwhile, we admitted that the SEM imaging of the calcined V 2 O 5 microspheres might not be sufficient to fully reveal the optimal structures; details such as effective particle surface area and contact area between the particle and substrate may also play a non-negligible role in the electrochemical process.…”

“…Scanning electrochemical cell microscopy (SECCM), as one emerging powerful technique for single-entity electrochemical study, uses a micro-/nanopipette filled with an electrolyte solution as a probe and obtains spatially resolved electrochemistry at nanointerfaces. − Compared to scanning electrochemical microscopy, SECCM has the merit of direct electrochemical visualization, and electrode materials are exposed to the reaction medium only when meniscus contact forms. In the past decade, this technique has been utilized to unravel many electrochemical processes, ranging from (photo)­electrocatalysis − to particle deposition, , dissolution, and bubble nucleation. − In energy storage materials, SECCM has been employed to study the intercalation at individual particles, such as LiFePO 4 , − LiMn 2 O 4 , LiCoO 2 , , NCM, and TiO 2 . However, these SECCM investigations of single particles are limited to nanomaterials with high structural stability.…”

“…24−27 In energy storage materials, SECCM has been employed to study the intercalation at individual particles, such as LiFePO 4 , 28−31 LiMn 2 O 4 , 32 LiCoO 2 , 33,34 NCM, 30 and TiO 2 . 35 However, these SECCM investigations of single particles are limited to nanomaterials with high structural stability.…”

Imaging and quantifying the chemical communication between single particles in metal alloy

“…[49][50][51] In light of this, direct in-situ measurements of local electrochemical activity are necessary to complement the in-situ observation of surface deposition/dissolution and to rigorously develop a physical model for chemical communication. An intriguing direction for future research would be to investigate the use of local complementary probing techniques, such as nanopipet methods in a combined opto-electrochemical approach, [52][53][54][55] to supplement optical observations with direct local electrochemical measurements.…”