TiS₂ as an Advanced Conversion Electrode for Sodium‐Ion Batteries with Ultra‐High Capacity and Long‐Cycle Life

Abstract

Titanium disulfide (TiS2) is investigated as an advanced conversion electrode for sodium (Na)‐ion batteries (NIB) in an ether‐based electrolyte (NaPF6/glyme (DME)). The as‐prepared TiS2 demonstrates a high reversible capacity of 1040 mA h g−1 at 0.2 A g−1 with the capacity contribution of 521 mA h g−1 in the voltage region below 1.0 V (vs Na/Na+), remarkable initial coulombic efficiency of 95.9% and superior rate capability of 621 mA h g−1 at 40 A g−1. The high conductivity of the Ti‐based compounds and nanosized particles generated by chemical conversion reactions could minimize the entropic barrier for the reversible conversion, resulting in high reversibility and ultrafast charge/discharge ability of the electrode. Moreover, with its strong ability to adsorb soluble polysulfide intermediates, the as‐prepared TiS2 electrode exhibits superior cycling stability over 9000 cycles, serving as a stable and ultra‐high capacity conversion electrode for NIBs.

Efficient Na‐Ion Storage in 2D TiS2 Formed by a Vapor Phase Anion‐Exchange Process

“…15-0853). [20] Consistent with the XRD result, a clear lattice fringe with an interlayer distance of 0.60 nm, corresponding to the (001) plane of the layered TiS 2 , [32] is easily observed in the edge side of the nanospheres (Figure 2g). Besides, some conformal coated carbon layers around the TiS 2 lattices are also detected, which derived from the in-situ carbonization of the carbon-rich HsGDY networks (Figure 2g).…”

“…[28][29][30][31][32] Recently, TiS 2 has been explored as a conversion anode material for NIBs in an ether-based electrolyte, which resulted in a new breakthrough in TiS 2 in electrochemical performance. [20] It is well known that the storage capability of electrode materials is highly related to their active surface area. Nanostructure engineering of 2D TiS 2 nanocrystals in a rationally-designed carbon network is an attractive approach to maximize the active storage sites, minimize the ion diffusion distance, and suppress the polysulfide dissolution, all of which can improve capacity utilization.…”

“…In addition to nanostructure engineering of TMDs, it is also vital to suppress the dissolution of polysulfide intermediates induced by their poor stability during conversion reactions. [20] In an effort to ameliorate this issue, there are two possible strategies: physical confinement by nanostructured carbon materials [21,22] or chemical binding by additional anchoring materials. [23,24] With regards to TMDs, 2D layered titanium disulfide (TiS 2 ) with a strong binding energy toward polysulfide has demonstrated its effectiveness in Li-S batteries, which make it a competent candidate for NIBs with limited polysulfide-shuttle.…”

Roles of Ti in Electrode Materials for Sodium-Ion Batteries

“…TiS 2 has been investigated as an anode material for sodium ion battery for similar reasons as TiO 2 . Four electrons can be transferred through electrochemical conversion of TiS 2 to metallic Ti, leading to a theoretical capacity of 957 mA h/g (Tao et al, 2018).…”

“…Obviously, after activation of the electrode material in the initial cycle, Ti 4+ was reduced to a lower valence state (Ti 0 ) in the subsequent cycles, whereas conversion of NaTiS 2 to Ti metal and Na 2 S was not seen with the cut off voltage of 1 V (Liu et al, 2016). DFT calculations proposed that TiS 2 is a semi-conductor in nature whereas NaTiS 2 and Ti 0.77 S are more metallic, which can enhance the electronic conductivity of the electrode, leading to the excellent rate capacity of 621 mAh/g at 40 A/g (Tao et al, 2018), Figure 2C.…”