Laboratory X-ray Microscopy Study of Microcrack Evolution in a Novel Sodium Iron Titanate-Based Cathode Material for Li-Ion Batteries

Viktor Shapovalov,Kristina Kutukova,Christian Heubner,Igor Shukaev,Vera Butova,Alexander Guda,Alexander Soldatov,Ehrenfried Zschech,Sebastian Maletti

doi:10.3390/cryst12010003

Abstract

The long-term performance of batteries depends strongly on the 3D morphology of electrode materials. Morphological changes, i.e., particle fracture and surface deterioration, are among the most prominent sources of electrode degradation. A profound understanding of the fracture mechanics of electrode materials in micro- and nanoscale dimensions requires the use of advanced in situ and operando techniques. In this paper, we demonstrate the capabilities of laboratory X-ray microscopy and nano X-ray computed tomography (nano-XCT) for the non-destructive study of the electrode material’s 3D morphology and defects, such as microcracks, at sub-micron resolution. We investigate the morphology of Na0.9Fe0.45Ti1.55O4 sodium iron titanate (NFTO) cathode material in Li-ion batteries using laboratory-based in situ and operando X-ray microscopy. The impact of the morphology on the degradation of battery materials, particularly the size- and density-dependence of the fracture behavior of the particles, is revealed based on a semi-quantitative analysis of the formation and propagation of microcracks in particles. Finally, we discuss design concepts of the operando cells for the study of electrochemical processes.

Highlights

The development of new materials for efficient and durable systems used for energy storage and conversion is crucial for modern and future energy technologies and transport, which heavily rely on the use of renewable power sources, hybrid, and all-electric vehicles [1,2,3]
The performance of batteries strongly depends on the 3D microstructure and morphology of the porous electrode materials [4,5]
Microcrack formation and propagation in particles that form the electrodes lead to rupture and reformation of the solid electrolyte interphase (SEI), which is accompanied by a capacity decline in full cells

Summary

Introduction

The development of new materials for efficient and durable systems used for energy storage and conversion is crucial for modern and future energy technologies and transport, which heavily rely on the use of renewable power sources, hybrid, and all-electric vehicles [1,2,3]. The performance of batteries strongly depends on the 3D microstructure and morphology of the porous electrode materials [4,5]. Morphological changes, i.e., particle fracture and surface deterioration, are among the most prominent sources of electrode degradation and eventual irreversible capacity loss [12,13]. These effects play a major role in electrode failure at high current loads, especially in materials where the reversible storage of alkali ions is accompanied by high volume changes [14]. Disconnected particles and accelerating chemical reactions caused by the newly formed SEI result in increased impedance and reduced battery performance

Methods

Discussion

Conclusion