## 8 Applications of Two-Dimensional Nanoscale SnS
via a chemical synthesis method utilising SnCl\({}_{2}\) over TiO\({}_{2}\) spheres followed by the carbonisation of glucose to form a TiO\({}_{2}\)/SnS/C composite with a SnS layer of around 10-15 nm thickness. A capacity retention of 95.6% was found after 2500 cycles at 1 A g\({}^{-1}\) with a rate capability of 357.2 mAh g\({}^{-1}\). The layering of SnS between TiO\({}_{2}\) and carbon moderates volume expansion and helps maintain structural integrity during cycling, which is shown by the low maximum expansion rate of the first lithiation (11.5%) [163]. [PERSON] et al. have developed a vertically aligned SnS nanosheet on a stainless-steel electrode via pulsed laser deposition. The SnS nanosheets had a thickness of 10-15 nm with lateral sizes of the order of hundreds of nm. A stable capacity of 560 mAh g\({}^{-1}\) over 50 cycles with a rate capability of 511 mAh g\({}^{-1}\) at 10 C s\({}^{-1}\) m\({}^{-2}\) current density was obtained, with the high capacity due to the large surface area. The stable cycle retention was attributed to the SnS retaining its structure after multiple alloying reactions, as determined via FE SEM--the powdered SnS had a reduced discharge capacity from 815 mA h g\({}^{-1}\) to 163 mA h g\({}^{-1}\). The 2D SnS had a higher capacity than SnS powder and thin film electrodes. The high performance of the 2D SnS nanosheets were attributed to efficient transport provided by the 2D electronic pathway [161]. Lower dimensional SnS, including nanorods [162, 165] and quantum dots [166], have also been utilised for lithium-ion batteries. SnS has also been used in the creation of sodium-ion batteries, with SnS nanosheets attached to an interconnected carbon nanotube network; the nanosheets obtained appeared of the order tens to hundreds of nm, with a 5.5 nm carbon layer and carbon nanotubes of 10 nm in diameter. The composite was prepared via a hydrothermal method and subsequent chemical polymerisation. The nanosheet and CNT architecture was found to enhance the ion and electron diffusion kinetics, with the nanosheets reducing the ion diffusion path, the nanotubes enhancing transfer, and the carbon layer enhancing conductivity and reducing volume expansion. A high specific capacity of 494.9 mAh g\({}^{-1}\) was maintained after 400 cycles at 1 A g\({}^{-1}\) for use in lithium-ion batteries with a high reversible capacity of 582.6 mAh g\({}^{-1}\) at 0.2 A g\({}^{-1}\) and long-term cycling performance of  
Figure 15: (**a**) SEM image of SnS nanosheet/rGO composite; (**b**) schematic of composite; and (**c**) rate performance of different current densities. Adapted with permission from _RSC Adv._, **2015**, _58_, 46941–46946. 243.3 mAh g\({}^{-1}\) over 400 cycles at 0.5 A g\({}^{-1}\) for sodium-ion batteries [167]. [PERSON] et al. have produced a SnS/graphene hybrid via a hydrothermal route with a SnS\({}_{2}\)/graphene composite for reference for use in sodium-ion batteries. The SnS undergoes a phase transition when heated under argon. The SnS/graphene composite showed a stable capacity of 940 mAh g\({}^{-1}\) after 50 cycles and a current density of 30 mA g\({}^{-1}\). The SnS layer structure and composite structure allows for the buffering of volume changes [168]. One-dimensional SnS rods [169] and SnS nanoparticles [170] have also been utilised for sodium-ion batteries. Potassium-ion batteries based on SnS with rGO modifications have been prepared by [PERSON] et al. via a solvothermal reaction and heat treatment. The anode produced delivered a capacity of 565 mAh g\({}^{-1}\) at 100 mA g\({}^{-1}\). The storage mechanisms were determined via cyclic voltammetry and galvanostatic cycling in the ranges 0.001-2 V and 0.3-2 V vs. K\({}^{+}\)/K. The alloying reaction at 0.43 V between Sn and K is: Sn + xK\({}^{+}\) +xe\({}^{-}\)\(\rightarrow\) KvSn.