Issue 43, 2023

Visualizing asymmetric phase separation driven by surface ionic diffusion in lithium titanate

Abstract

Phase transition kinetics of battery electrodes is a critical factor affecting power and durability. Li4Ti5O12 exhibits high-rate capability despite low bulk lithium diffusivities and kinetic barriers to phase separation. However, the phase transition and high-rate capability of mechanisms continue to remain unclear. Here, we reveal spatially asymmetric phase separation during lithiation and delithiation through real-time monitoring of nanoscale lithium distribution. Surface ionic diffusion, which exhibits intermediate diffusion kinetics for the delithiated Li4Ti5O12 and lithiated Li7Ti5O12 phases, serves as the primary driving force for asymmetric phase separation. During lithiation, Li7Ti5O12 with lower ionic diffusivity forms on the particle shell by surface diffusion even if the particle is not completely covered with an electrolyte; conversely, the core–shell structure does not form during delithiation. Microscale asymmetric phase separation and different ionic diffusivities between the two phases lead to asymmetric polarization in charge–discharge measurements. Preferential Li-ion diffusion at grain boundaries is also observed. This study highlights the feasibility of surface and grain boundary engineering for mediating ionic diffusion.

Graphical abstract: Visualizing asymmetric phase separation driven by surface ionic diffusion in lithium titanate

Supplementary files

Article information

Article type
Communication
Submitted
18 Aug 2023
Accepted
23 Oct 2023
First published
30 Oct 2023

J. Mater. Chem. A, 2023,11, 23243-23248

Visualizing asymmetric phase separation driven by surface ionic diffusion in lithium titanate

Y. Nomura, K. Yamamoto and T. Hirayama, J. Mater. Chem. A, 2023, 11, 23243 DOI: 10.1039/D3TA04956F

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements