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Probing three-dimensional sodiation-desodiation equilibrium in sodium-ion batteries by in situ hard X-ray nanotomography.

Wang J, Eng C, Chen-Wiegart YC, Wang J - Nat Commun (2015)

Bottom Line: Efforts to relieve this problem are reliant on the understanding of electrochemical and structural degradation.We find an unusual (de)sodiation equilibrium during multi-electrochemical cycles.The superior structural reversibility during 10 electrochemical cycles and the significantly different morphological change features from comparable lithium-ion systems suggest untapped potential in sodium-ion batteries.

View Article: PubMed Central - PubMed

Affiliation: National Synchrotron Light Source II, Brookhaven National Laboratory, Building 743 Ring Road, Upton, New York 11973, USA.

ABSTRACT
Materials degradation-the main limiting factor for widespread application of alloy anodes in battery systems-was assumed to be worse in sodium alloys than in lithium analogues due to the larger sodium-ion radius. Efforts to relieve this problem are reliant on the understanding of electrochemical and structural degradation. Here we track three-dimensional structural and chemical evolution of tin anodes in sodium-ion batteries with in situ synchrotron hard X-ray nanotomography. We find an unusual (de)sodiation equilibrium during multi-electrochemical cycles. The superior structural reversibility during 10 electrochemical cycles and the significantly different morphological change features from comparable lithium-ion systems suggest untapped potential in sodium-ion batteries. These findings differ from the conventional thought that sodium ions always lead to more severe fractures in the electrode than lithium ions, which could have impact in advancing development of sodium-ion batteries.

No MeSH data available.


Related in: MedlinePlus

Comparison of Sn anodes in NIB and LIB systems.(a) 3D visualization of Sn particles at the first lithiation–delithiation process. Particles are coloured on particle size to assist in data analysis and view. (b) Schematic illustration showing the difference of Sn microstructural change in NIB and LIB. For NIB, the sodiation leads to obvious microstructural cracks, but the desodiation process only shrinks the volume with negligible pulverization. In contrast, the microstructural change in LIB predominantly occurs during the delithiation process, with the formation of many pores and pulverization. The feature size distribution of Sn particles in (c) LIBs and (d) NIBs confirms the sketch in b. (e,f) 3D quantitative comparison of (e) volume, (f) specific area, (g) curvature in NIBs and (h) curvature in LIBs. Scale bar, 10 μm.
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f7: Comparison of Sn anodes in NIB and LIB systems.(a) 3D visualization of Sn particles at the first lithiation–delithiation process. Particles are coloured on particle size to assist in data analysis and view. (b) Schematic illustration showing the difference of Sn microstructural change in NIB and LIB. For NIB, the sodiation leads to obvious microstructural cracks, but the desodiation process only shrinks the volume with negligible pulverization. In contrast, the microstructural change in LIB predominantly occurs during the delithiation process, with the formation of many pores and pulverization. The feature size distribution of Sn particles in (c) LIBs and (d) NIBs confirms the sketch in b. (e,f) 3D quantitative comparison of (e) volume, (f) specific area, (g) curvature in NIBs and (h) curvature in LIBs. Scale bar, 10 μm.

Mentions: Considering the larger ionic radius, the excellent structural stability of Sn in NIB is surprising, which inspired us to perform a comparative study. Compared with Sn in NIB, severe microstructural change accompanied with large amounts of pores mainly occurs at the delithiation process in LIB, not the lithiation step (Fig. 7a,b, Supplementary Movie 4). When Li ions are initially inserted into Sn anode, in spite of volume expansion, LixSn shows low microstructural damage, but Li-ions extraction induces enormous morphology pulverization, featuring many pores formation. In contrast, Na-ion insertion results in large volume expansion and fracture in NIB, whereas Na-ion extraction only induces the volume shrinkage with negligible pulverization and maintains microstructural integrity. This difference in microstructural change can be also revealed by the feature size distribution (Fig. 7c,d). The smallest feature size in LIB corresponds to the delithiated process, while it corresponds to the sodiated step for NIB. Despite Sn anodes showing larger volume expansion in NIBs (Fig. 7e), the specific area parameter suggests a microstructural equilibrium after the first sodiation (Fig. 7f). To understand the origin of microstructural equilibrium, the surface curvature evolution was illustrated in Fig. 7g,h. Since concave features play a major role in affecting the microstructural stability, the continuous increase at the both lithiation and delithiation process indicates that the microstructure cannot reach equilibrium after the first cycle for LIB, so further microstructure damage may continue during the following cycles. In contrast, the significant increase after the sodiation process and the following decrease after the desodiation step for the concave features indicate that the microstructures reach mechanical equilibrium at the end of the first sodiation. As a result, the superior electrochemical stability at the following cycles can be obtained in NIBs. It should be noted that this comparative study is to show the significantly different morphological features of Sn in NIB and LIB. No cycle performance is directly compared in this work. It should be mentioned that this in situ 3D study and the quantitative analysis are based on X-ray imaging technology to provide microstructural information in 3D and reveal the large-scale electrode behavior, which can represent the entire battery electrode. Some nanostructural change may also exist at higher resolution scale which is beyond the existing hard X-ray TXM imaging resolution limitation3334, and is not discussed in this work. Technological advances in lensless coherent diffraction imaging method can achieve higher spatial resolution, and will be potentially applied in nanostructural materials research35.


Probing three-dimensional sodiation-desodiation equilibrium in sodium-ion batteries by in situ hard X-ray nanotomography.

Wang J, Eng C, Chen-Wiegart YC, Wang J - Nat Commun (2015)

Comparison of Sn anodes in NIB and LIB systems.(a) 3D visualization of Sn particles at the first lithiation–delithiation process. Particles are coloured on particle size to assist in data analysis and view. (b) Schematic illustration showing the difference of Sn microstructural change in NIB and LIB. For NIB, the sodiation leads to obvious microstructural cracks, but the desodiation process only shrinks the volume with negligible pulverization. In contrast, the microstructural change in LIB predominantly occurs during the delithiation process, with the formation of many pores and pulverization. The feature size distribution of Sn particles in (c) LIBs and (d) NIBs confirms the sketch in b. (e,f) 3D quantitative comparison of (e) volume, (f) specific area, (g) curvature in NIBs and (h) curvature in LIBs. Scale bar, 10 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4491187&req=5

f7: Comparison of Sn anodes in NIB and LIB systems.(a) 3D visualization of Sn particles at the first lithiation–delithiation process. Particles are coloured on particle size to assist in data analysis and view. (b) Schematic illustration showing the difference of Sn microstructural change in NIB and LIB. For NIB, the sodiation leads to obvious microstructural cracks, but the desodiation process only shrinks the volume with negligible pulverization. In contrast, the microstructural change in LIB predominantly occurs during the delithiation process, with the formation of many pores and pulverization. The feature size distribution of Sn particles in (c) LIBs and (d) NIBs confirms the sketch in b. (e,f) 3D quantitative comparison of (e) volume, (f) specific area, (g) curvature in NIBs and (h) curvature in LIBs. Scale bar, 10 μm.
Mentions: Considering the larger ionic radius, the excellent structural stability of Sn in NIB is surprising, which inspired us to perform a comparative study. Compared with Sn in NIB, severe microstructural change accompanied with large amounts of pores mainly occurs at the delithiation process in LIB, not the lithiation step (Fig. 7a,b, Supplementary Movie 4). When Li ions are initially inserted into Sn anode, in spite of volume expansion, LixSn shows low microstructural damage, but Li-ions extraction induces enormous morphology pulverization, featuring many pores formation. In contrast, Na-ion insertion results in large volume expansion and fracture in NIB, whereas Na-ion extraction only induces the volume shrinkage with negligible pulverization and maintains microstructural integrity. This difference in microstructural change can be also revealed by the feature size distribution (Fig. 7c,d). The smallest feature size in LIB corresponds to the delithiated process, while it corresponds to the sodiated step for NIB. Despite Sn anodes showing larger volume expansion in NIBs (Fig. 7e), the specific area parameter suggests a microstructural equilibrium after the first sodiation (Fig. 7f). To understand the origin of microstructural equilibrium, the surface curvature evolution was illustrated in Fig. 7g,h. Since concave features play a major role in affecting the microstructural stability, the continuous increase at the both lithiation and delithiation process indicates that the microstructure cannot reach equilibrium after the first cycle for LIB, so further microstructure damage may continue during the following cycles. In contrast, the significant increase after the sodiation process and the following decrease after the desodiation step for the concave features indicate that the microstructures reach mechanical equilibrium at the end of the first sodiation. As a result, the superior electrochemical stability at the following cycles can be obtained in NIBs. It should be noted that this comparative study is to show the significantly different morphological features of Sn in NIB and LIB. No cycle performance is directly compared in this work. It should be mentioned that this in situ 3D study and the quantitative analysis are based on X-ray imaging technology to provide microstructural information in 3D and reveal the large-scale electrode behavior, which can represent the entire battery electrode. Some nanostructural change may also exist at higher resolution scale which is beyond the existing hard X-ray TXM imaging resolution limitation3334, and is not discussed in this work. Technological advances in lensless coherent diffraction imaging method can achieve higher spatial resolution, and will be potentially applied in nanostructural materials research35.

Bottom Line: Efforts to relieve this problem are reliant on the understanding of electrochemical and structural degradation.We find an unusual (de)sodiation equilibrium during multi-electrochemical cycles.The superior structural reversibility during 10 electrochemical cycles and the significantly different morphological change features from comparable lithium-ion systems suggest untapped potential in sodium-ion batteries.

View Article: PubMed Central - PubMed

Affiliation: National Synchrotron Light Source II, Brookhaven National Laboratory, Building 743 Ring Road, Upton, New York 11973, USA.

ABSTRACT
Materials degradation-the main limiting factor for widespread application of alloy anodes in battery systems-was assumed to be worse in sodium alloys than in lithium analogues due to the larger sodium-ion radius. Efforts to relieve this problem are reliant on the understanding of electrochemical and structural degradation. Here we track three-dimensional structural and chemical evolution of tin anodes in sodium-ion batteries with in situ synchrotron hard X-ray nanotomography. We find an unusual (de)sodiation equilibrium during multi-electrochemical cycles. The superior structural reversibility during 10 electrochemical cycles and the significantly different morphological change features from comparable lithium-ion systems suggest untapped potential in sodium-ion batteries. These findings differ from the conventional thought that sodium ions always lead to more severe fractures in the electrode than lithium ions, which could have impact in advancing development of sodium-ion batteries.

No MeSH data available.


Related in: MedlinePlus