Structural and chemical evolution in layered oxide cathodes of lithium-ion batteries revealed by synchrotron techniques

Abstract

Rechargeable battery technologies have revolutionized the electronics, transportation, and grid energy storage. While many materials are being researched for battery applications, layered transition metal oxides (LTMO) are the dominating cathode candidate with remarkable electrochemical performance. Yet, daunting challenges persist in the quest for further battery developments targeting lower cost, longer lifespan, improved energy density, and enhanced safety. This is in part due to the intrinsic complexity in real-world batteries, featuring sophisticated interplay among microstructural, compositional, and chemical heterogeneities, which motivates tremendous research efforts using state-of-the-art analytical techniques. In this research field, synchrotron techniques are identified as a suite of effective methods for advanced battery characterization in a nondestructive manner with sensitivities to the lattice, electronic, and morphological structures. This article provides a holistic overview of the cutting-edge developments in synchrotron-based research on LTMO battery cathode materials. We discuss the complexity and evolution of LTMO’s material properties upon battery operation and review recent synchrotron-based research works that address the frontier challenges and provide novel insights in this field. Finally, we formulate a perspective on the future directions of synchrotron-based battery research, involving the next-generation X-ray facilities and advanced computational developments.

Heterogeneous Reaction Activities and Statistical Characteristics of Particle Cracking in Battery Electrodes

“…The heterogeneous nature of electrochemical reactions and mechanical degradation places a daunting challenge in electron and X-ray characterizations. − Recent large-scale electrode studies have uncovered that particle cracking is highly heterogeneous in composite electrodes. There are fundamental reasons and practical implications of such heterogeneity, which is ubiquitous even in the best-optimized commercial battery electrodes. ,− Figure exemplifies such heterogeneity in a section of a practical electrode containing thousands of active particles.…”

The significance of detecting imperceptible physical/chemical changes/reactions in lithium-ion batteries: a perspective

“…130–132 Generally, absorption, phase shift and scattering are the three different basic interactions between X-rays and matter, and scientists have derived various X-ray characterization techniques sensitive to the lattice structure, 133 electronic structure, 134 and micromorphology. 45 X-ray absorption spectroscopy (XAS) is used mainly to detect the surface and interface information about materials; 135,136 scanning transmission X-ray microscopy (STXM/TXM), 137,138 X-ray fluorescence (XRF) microscopy 139,140 and X-ray diffraction imaging (CXDI) 141,142 are usually used to indicate microstructures; and X-ray diffraction, 143,144 hard X-ray absorption spectroscopy (XAS) 145,146 and pair distribution function (PDF) 147,148 are used to characterize the bulk structure of materials. Detailed characteristic information is summarized in Fig.…”

“…35–39 Furthermore, when combined with big data technology, synchrotron-based characterization can in situ reconstruct the three-dimensional (3D) structure information about, element distribution of and valence information about electrode materials, 40–43 benefiting the detection of the imperceptible physical/chemical change/reaction that occurs on/between the electrodes and electrolyte. 44–46 The information obtained from synchrotron radiation characterization could significantly help in understanding the corresponding relationship between the macroscopic battery performance and the microscopic material structure evolution. 47–49…”

Data-Driven Lithium-Ion Battery Cathode Research with State-of-the-Art Synchrotron X-ray Techniques

“…This process is reversed when the battery is being discharged. The physical back-and-forth migration of lithium ions in the system during repeated battery cycling leads to structural evolutions across the scales of the lattice, particle, and electrode, and eventually results in the battery degradation or even failure. ,, Therefore, three-dimensional micromorphology investigation is critical to understanding the multiscale structural failure in the battery. The results could inform the design of new materials and chemistries with improved structural robustness.…”

“…18,19 Synchrotron X-ray techniques have demonstrated unique advantages with excellent resolution and sensitivity to structural, chemical, and morphological characteristics of the battery materials. 20 These methods in different experimental modalities (Figure 1) can probe the lattice structure, electronic structure, chemical valence state, and multiscale morphology with high efficiency and precision. At the same time, they bring enormous challenges in task-specific data reduction, analysis, and interpretation.…”