Journal
CARBON ENERGY
Volume 4, Issue 2, Pages 129-141Publisher
WILEY
DOI: 10.1002/cey2.141
Keywords
lithium-ion battery; SEI film growth; SiOx; stress; valence gradient
Categories
Funding
- Fujian Natural Science Foundation for Distinguished Young Scholars [2020J06042]
- Solar Energy Conversion & Energy Storage Engineering Technology Innovation Platform [2018L3006]
- National Natural Science Foundation of China [61804030]
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Optimizing the Si-valence gradient in SiOx composites can help mitigate volume strain during lithium insertion/extraction, leading to enhanced electrochemical performance and high cycling stability.
Relieving the stress or strain associated with volume change is highly desirable for high-performance SiOx anodes in terms of stable solid electrolyte interphase (SEI)-film growth. Herein, a Si-valence gradient is optimized in SiOx composites to circumvent the large volume strain accompanied by lithium insertion/extraction. SiOx@C annealed at 850 degrees C has a gentle Si-valence gradient along the radial direction and excellent electrochemical performances, delivering a high capacity of 506.9 mAh g(-1) at 1.0 A g(-1) with a high Coulombic efficiency of similar to 99.8% over 400 cycles. Combined with the theoretical prediction, the obtained results indicate that the gentle Si-valence gradient in SiOx@C is useful for suppressing plastic deformation and maintaining the inner connection integrity within the SiOx@C particle. Moreover, a gentle Si-valence gradient is expected to form a stress gradient and affect the distribution of dangling bonds, resulting in local stress relief during the lithiation/delithiation process and enhanced Li-ion kinetic diffusion. Furthermore, the lowest interfacial stress variation ensures a stable SEI film at the interface and consequently increases cycling stability. Therefore, rational design of a Si-valence gradient in SiOx can provide further insights into achieving high-performance SiOx anodes with large-scale production.
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