Nanosized Ti ₄ O ₇ supported on carbon nanotubes composite modified separator for enhanced electrochemical properties of lithium sulfur battery

Abstract

Summary The novel lithium sulfur (Li‐S) battery is widely concerned owing to its ultrahigh theoretical energy density of 2600 Wh/kg. However, its commercial application has been obstructed by the rapid decline of capacity and short cycle life, which is mainly because of the dissolution behavior of polysulfides into electrolyte solution and subsequently continual shuttling effect. Some strategies including carbon carriers for loading sulfur, modification of electrolyte and overall structure design of cell are brought forward to overcome the inherent defects of Li‐S battery. Modified separators with multifunctional layer are also investigated extensively and benefit from their simple preparation method and enhanced electrochemical properties. Herein, nanosized Ti4O7 supported on mildly oxidized carbon nanotubes (oCNTs‐Ti4O7) composite was synthetized and coated on the surface of separator to form modified layer, which is combined with the electrically conductive network structure of CNTs and effective adsorption of Ti4O7 nanoparticles. Compared with common separator, the modified separator with oCNTs‐Ti4O7 layer can significantly improve the utilization of active substances as an additional current collector and restrain the shuttling effect of polysulfides by combination of physical obstruction and chemical adsorption. The Li‐S battery has made great enhancements in electrochemical properties including cycle and rate performance. In particular, the cell using oCNTs‐Ti4O7 separator has released specific discharge capacities of 888 and 658 mAh/g at a current density of 0.5C for the 1st and 250th cycle with a capacity retention of 74.1%. In the rate performance test, a discharge capacity of 586 mAh/g is still remained even at a high current density of 2C. Meanwhile, the test results of diffusion behavior indicate that the modified layer would not affect the normal transmission of lithium ions.

Recent advances in modified commercial separators for lithium–sulfur batteries

“…Essentially, adding MWCNTs made TiO a viable modifier for LSB separators, allowing an astoundingly low capacity fade rate of 0.057% per cycle. Similarly, recent studies combined various CNTs with oxygen-rich MnO nanoflakes, 230 TiO 2 , 231 Nb 2 O 5 , 232 MnO, 233 and Ti 4 O 7 234 to enhance specific capacity while also significantly improving polysulfide rejection. Wang et al 235 sandwiched 1D SWCNTs between 2D V 2 C/V 2 O 5 nanosheet layers to prevent the nanosheets from agglomerating, resulting in a maximum number of active sites for polysulfide adsorption.…”

A well-dispersed OV-NiCo2O4 nanosphere modified separator for Li–S batteries

“…In contrast, polar materials, such as transition metal oxides, help in efficiently immobilizing LiPSs and promoting their conversion. In recent years, some reports have shown that metal oxides of inorganic polar compounds, such as TiO 2 , 12 Ti 4 O 7 , 13 V 2 O 5 , 14 MnO 2 , 15 and SnO 2 , 16 can efficiently inhibit the shuttle effect benefiting from the ability to effectively trap LiPSs through strong chemical interactions. However, the conductivity of these polar compounds is generally lower than that of carbon materials, resulting in low sulfur utilization and poor rate performance.…”

Synergistic effect of adsorption and electrocatalysis of CoO/NiO heterostructure nanosheet assembled nanocages for high-performance lithium–sulfur batteries

“…18,19 Recently, a variety of functional materials have been applied to modify the separators of Li–S batteries. 20–22 It has been reported that polar transition metal oxides (TMOs), such as Co 3 O 4 , 23 Nb 2 O 5 , 24 NiO, 25 Ti 4 O 7 , 26 oxygen-deficient TiO 2 , 27 TiO, 28 and ZnO, 29 can effectively anchor LiPSs and even promote the redox kinetics of LiPSs. Among these TMOs, CoO has gained great attention due to its strong chemical adsorption to LiPSs.…”