Atomic-layer-deposited TiO2-SnZnO/carbon nanofiber composite as a highly stable, flexible and freestanding anode material for lithium-ion batteries

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2018-04, Vol.338, p.72-81
• Main Authors: Joshi, Bhavana, Samuel, Edmund, Kim, Min-Woo, Park, Sera, Swihart, Mark T., Yoon, Woo Young, Yoon, Sam S.
• Format: Article
• Language: English
• Subjects: Anode; Atomic layer deposition; Carbon nanofiber; Electrospinning; Lithium-ion battery; SnZnO
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2018.01.004

•A highly stable, freestanding, and flexible anode material for lithium-ion batteries (LIB) was synthesized into a nanofiber.•TiO2 was coated on a SnZnO/carbon nanofiber using atomic layer deposition (ALD).•Because of the buffering TiO2 layer, no signs of anode degradation even after 700 cycles.•These durable and lightweight LIBs should promote the use of ALD in the battery industry. We demonstrate the synthesis of a highly stable, freestanding and flexible anode material for lithium-ion batteries created by depositing a conformal coating of TiO2 on a SnZnO/carbon nanofiber (CNF) composite using atomic layer deposition. The term SnZnO is used here because metallic Sn is observed in the SnZnO/CNF composites after annealing under argon gas. The elemental composition of the material was confirmed by energy-dispersive X-ray spectroscopy, while the oxidation states of the elements were determined by X-ray photoelectron spectroscopy. Cross-sectional transmission electron microscopy showed that the core regions of the composite nanofibers were almost uniformly covered by a TiO2 shell. The specific capacities of the TiO2-coated and uncoated samples at a high current density (5C) were 413 and 159 mAh·g−1, respectively. An analysis of the surface morphology after cycling indicated that the stability of the solid electrolyte interface layer increased after the formation of the protective conformal TiO2 layer. As a result, no signs of anode degradation were observed even after 700 cycles at a current density of 5C. We attribute this exceptional stability to the buffering of the anode material by the protective coating during volumetric expansion.