Fabrication and Electrochemical Performance of TiO₂–TiN/Sn–SnO₂ Composite Films on Ti for LIB Anodes with High Capacity and Excellent Conductivity

Abstract

cameras and smartphones to electric vehicles and power storage systems, which has placed higher performance requirements on them. [3][4][5] Graphite is conventionally used as an LIB anode for economic reasons, although its theoretical specific capacity of 272 mAh g −1 is relatively low. [6,7] However, as the capacity of LIBs is improved, they exhibit serious safety issues. This is because conventional graphite anodes (0.1 V vs Li + /Li) experience lithium dendrite growth upon repeated charging/discharging. TiO 2 materials have a high working potential (1.7 V vs Li + /Li) and chemical and thermal stability; thus, they are suitable for replacing conventional graphite anodes to improve the safety of LIBs. [8,9] Moreover, nanostructured TiO 2 has a large surface area, which promotes the insertion/removal of Li + when used as an electrode material. Several types of nanostructures can be prepared, including hollow/micro/nanospheres, [10,11] nanotubes, [12] and nanosheets. [13] Because of the low electrical conductivity of TiO 2 , various TiO 2 -based composite materials have been developed to improve its physical properties, such as nanoporous TiO 2 /Co 3 O 4 , [14] TiO 2 -C/MnO 2 nanowire arrays, [15] and TiO 2 / MoO 3 nanotubes. [16] However, such materials have complicated manufacturing processes, and their capacities are insufficient for commercial use as anode materials.Another central issue for traditional graphite anodes is their low power density, which hinders their application in LIBs for electric vehicles. Si is often considered the most appealing anode material for next-generation LIBs owing to its high theoretical specific capacity of 4200 mAh g −1 . [17] However, the commercialization of Si-based anode materials is restricted by their low intrinsic electrical conductivity (10 −5 to 10 −3 S cm −1 ), low Li-ion diffusivity (10 −14 to 10 −13 cm 2 s −1 ), continuous growth of a solid electrolyte interphase, [18] high production cost, and extreme volume expansion of up to 300-400%. In contrast, Sn anodes possess a very high theoretical electrical conductivity (8.7 × 10 6 S m −1 ), comparable volumetric capacity (2020 mAh cm −3 ), and high availability for low-cost manufacturing. Unfortunately, they also exhibit a relatively large volumetric change during lithiation and delithiation (260% in Li 22 Sn 5 , corresponding to 994 mAh g −1 ). [19] Compared to Sn, SnO 2 has a lower volume expansion ratio (≈150%). However, the According to the requirements for anode materials of safe and high-capacity lithium-ion batteries (LIBs), various Sn/TiO 2 and SnO 2 /TiO 2 composite materials have been developed, but no reports have yet combined them by a simple fabrication method. Herein, a novel and simple approach is reported for the fabrication of nanoporous TiO 2 -TiN/Sn-SnO 2 composite films by successive Ti anodization and cathodic hybrid electrodeposition of Sn in a nitric acid-based aqueous solution containing Sn 2+ and/or Sn 4+ ions. The conductivity of the anodic TiO 2 -TiN composite films facilitates the simultaneou...

Bifunctional Urea–Polyethyleneimine‐Mediated Surface Engineering in SnO2 Electron‐Transport Layer for Efficient and Stable Organic Solar Cells

“…Notably, u‐ PEI10 exhibits the largest peak shift, signifying the strongest coordination with Sn atoms, as shown in Figure S5, Supporting Information. [ 56,57 ] This result is due to the reduced dipole moment caused by the increase in the degree of ethyl urea functionalization, as indicated by the DFT calculations presented in Figure 2d. Given that the stronger coordination implies enhanced oxygen‐vacancy passivation, the XPS analysis confirms the superior oxygen‐vacancy passivation capabilities of u‐ PEI10.…”

Nanowires-Assembled TiO2 Nanorods Anchored on Multilayer Graphene for High-Performance Anodes of Lithium-Ion Batteries

“…As Lithium-ion batteries (LIBs) have become more and more popularly used for electric vehicles, the enhancement of the energy density of LIBs is desired for longer distances on one charge [ 1 , 2 ]. Anode materials with high specific capacities have been widely researched [ 3 , 4 ] in order to replace commercial graphite, which has a specific capacity of 372 mAh g −1 . Another shortage of graphite anode is the lithium plating that easily occurs due to the low operation potential, which will cause a serious safety issue [ 5 , 6 ].…”