Issue 34, 2020

Oxygen defect chemistry for the reversible transformation of titanates for sizeable potassium storage

Abstract

Potassium-ion batteries (KIBs) are promising substitutes for lithium-ion batteries (LIBs) due to the earth-abundancy of potassium. However, practical KIB applications are hindered by slow diffusion kinetics and severe structural deterioration as the large cation is cycled in and out of the electrode. Here, a high-capacity electrode, oxygen-deficient loose-layered potassium titanate (LL-KTO), is synthesized to electrochemically store potassium via a “stacked ↔ sliced structural transformation” with net-zero structural deterioration. Owing to the positive structural energy compensation from oxygen vacancies, LL-KTO delaminates and restacks with K+ ions reversibly upon charging and discharging, in contrast to rigid oxide electrodes. As a result, it achieves a capacity of 201 mA h g−1 over 1800 cycles at 100 mA g−1, on par with values for titanium-oxide based LIBs. Peukert's constant, fractal dimension and host-to-guest ion ratio are further demonstrated as matrices to evaluate the performances of electrodes and show that LL-KTO with stacked ↔ sliced structural transformation pushes the kinetic boundary and approaches the thermodynamic limit of ion batteries. This work addresses the disadvantages of large ion storage by designing a new ion-storing mechanism and provides an important guide to design future energy storage systems and a method to compare electrode materials across different systems.

Graphical abstract: Oxygen defect chemistry for the reversible transformation of titanates for sizeable potassium storage

Supplementary files

Article information

Article type
Paper
Submitted
06 Jun 2020
Accepted
06 Aug 2020
First published
07 Aug 2020

J. Mater. Chem. A, 2020,8, 17550-17557

Oxygen defect chemistry for the reversible transformation of titanates for sizeable potassium storage

C. Lao, Q. Yu, J. Hu, N. Li, G. Divitini, H. Kim, W. (. Wang, Y. Liu, X. Chen and R. V. Kumar, J. Mater. Chem. A, 2020, 8, 17550 DOI: 10.1039/D0TA05685E

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