Boosting the cell performance of the SiOx@C anode material via rational design of a Si‐valence gradient

• Published in: Carbon energy 2022-03, Vol.4 (2), p.129-141
• Main Authors: Tao, Jianming, Yan, Zerui, Yang, Jiangshao, Li, Jiaxin, Lin, Yingbin, Huang, Zhigao
• Format: Article
• Language: English
• Subjects: Acids; Anodes; Electrochemistry; Electrode materials; Electrolytes; Film growth; Interface stability; Interfacial stresses; Lithium; lithium‐ion battery; Microscopy; Particle size; Plastic deformation; Radiation; SEI film growth; Silicon; SiOx; Solid electrolytes; Spectrum analysis; Strain; Stress; valence gradient
• ISSN: 2637-9368; 2637-9368
• DOI: 10.1002/cey2.141

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°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 ~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. It is highly desirable to develop a novel internal‐stress‐relief strategy to suppress SiOx expansion via design and optimization of Si valence in SiOx composites for high‐energy‐density lithium‐ion batteries. In our work, enhanced electrochemical performances of SiOx are obtained via optimizing the Si‐valence gradient from the viewpoint of stress evolution upon cycling.