Upgraded lithium storage performance of defect-rich Si@C anode assisted by Fe2O3-induced pseudocapacitance

• Published in: Electrochimica acta 2023-07, Vol.455, p.142430, Article 142430
• Main Authors: Yao, Yunfei, He, Zhiying, Xu, Xiangyang, Tong, Yuanlin, Chen, Dongsheng, Huang, Chenyu, Zhao, Hongye
• Format: Article
• Language: English
• Subjects: Defect-rich structure; Electrochemical performance; Interface-induced pseudocapacitance; Lithium storage; Silicon-based anode
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2023.142430

•Si-xFe/O@C anode was synthesized by facile hydrothermal-calcination approach.•Defect-rich structure upgrade lithiation and rate performance at high current.•Capacity of Si bonded with in situ Fe2O3 is superior to one blended raw Fe2O3 grains.•Considerable interfaces formed between in-situ Fe, LixSi and Li2O species.•Mechanism of interface-induced pseudocapacitance storage was discussed. Following a flowsheet comprised of a hydrothermal reaction and a dehydration/carbonization, Si-xFe/O@C anodes featured with Fe-doping and carbon encapsulation were assembled. Comparing with pure Si, Si disseminated with in situ generated nano-scaled ferric oxide (Fe2O3) particulates displays remarkably improved cyclic performance. Fe2O3 may induce amorphization and optimize electrical conductivity, by enhancing the formation of Fe and Li2O amidst charging-discharging cycles. The as-derived Fe phase benefits the transport and storage of lithium-ion and electrons. Meanwhile, numerous tiny interfaces can be constructed between Fe granules and adjacent LixSi or Li2O, and generate pseudocapacitance. After the carbonization of resorcinol-formaldehyde resin encapsulated on Si granules, core-shell structured Si-xFe/O@C particulates can be assembled. Owing to the synergism of defect-rich structure, carbon layer well-wrapped thereon and interfacial pseudocapacitance, these nanocomposite anode materials exhibit long cyclic and upgraded rate performance. After 200 cycles, Si-0.42Fe/O@C anode retains a capacity of 929 mAh·g−1 at 1 A·g−1 and 735 mAh·g−1 at 2 A·g−1. In the rate performance test operated at 5 A·g−1, a high current density, 844 mAh·g−1 could be released. Si-0.42Fe/O@C can be charged with a specific capacity exceeding 250 mAh·g−1 over the potential range of 0.75-3 V at various current densities, demonstrating the contribution of nano-Fe pseudocapacitance effect to the energy storage of Si anodes. [Display omitted] Dissembled in silicon clusters, Fe2O3 can enrich defects whilst enhance silicon amorphization and electrical conductivity, while the interfaces between Fe granules and adjacent LixSi or Li2O can induce pseudocapacitance. Owing to the synergism of defect-rich structure, robust carbon coating and interfacial pseudocapacitance, Si-xFe/O@C anode exhibits long cyclic and high-rate performance.