Boosted Lithium-Ion Transport Kinetics in n-Type Siloxene Anodes Enabled by Selective Nucleophilic Substitution of Phosphorus

• Published in: Nano-micro letters 2024-12, Vol.16 (1), p.219-20, Article 219
• Main Authors: Kim, Se In, Kim, Woong-Ju, Kang, Jin Gu, Kim, Dong-Wan
• Format: Article
• Language: English
• Subjects: Anodes; Atomic properties; Charge transfer; Charge transport; Crystal structure; Doping; Doping mechanism; Electrolytes; Electrons; Energy storage; Engineering; Ion storage; Ion transport; Kinetics; Li-ion batteries; Li-ion battery; Lithium-ion batteries; N-type siloxene; Nanoscale Science and Technology; Nanosheets; Nanotechnology; Nanotechnology and Microengineering; Optoelectronics; Oxidation; Rechargeable batteries; Substitutes; Tetrahedra; Two dimensional materials; Two-dimensional
• ISSN: 2311-6706; 2150-5551; 2150-5551
• DOI: 10.1007/s40820-024-01428-y

Highlights Extrinsic doping is proposed as a novel route to enhance the intrinsic properties of the two-dimensional oxidized Si nanosheet (namely, siloxene) anode for Li-ion batteries. Fabrication of P-doped n-type siloxene is revealed to be possible through selective nucleophilic substitution of Si atoms in siloxene with P atoms. Due to boosted charge transport kinetics, n-type siloxene (6.7 × 10 19 P atoms cm -3 ) exhibits the excellent storage performance (594 mAh g -1 after 500 cycles) even at 2000 mA g -1 . Doped two-dimensional (2D) materials hold significant promise for advancing many technologies, such as microelectronics, optoelectronics, and energy storage. Herein, n-type 2D oxidized Si nanosheets, namely n-type siloxene (n-SX), are employed as Li-ion battery anodes. Via thermal evaporation of sodium hypophosphite at 275 °C, P atoms are effectively incorporated into siloxene (SX) without compromising its 2D layered morphology and unique Kautsky-type crystal structure. Further, selective nucleophilic substitution occurs, with only Si atoms being replaced by P atoms in the O 3 ≡Si–H tetrahedra. The resulting n-SX possesses two delocalized electrons arising from the presence of two electron donor types: (i) P atoms residing in Si sites and (ii) H vacancies. The doping concentrations are varied by controlling the amount of precursors or their mean free paths. Even at 2000 mA g −1 , the n-SX electrode with the optimized doping concentration (6.7 × 10 19 atoms cm −3 ) delivers a capacity of 594 mAh g −1 with a 73% capacity retention after 500 cycles. These improvements originate from the enhanced kinetics of charge transport processes, including electronic conduction, charge transfer, and solid-state diffusion. The approach proposed herein offers an unprecedented route for engineering SX anodes to boost Li-ion storage.