Superlattices of SnS₂ with other TMDCs for Use as Electrodes in Li-Ion Batteries

In order to address the ever-increasing demand for better battery materials [1], we present a study exploring the potential of multi-layered superlattices made from 2D materials in order to understand the benefits and drawbacks such layered materials could have as potential device electrodes. Layered materials of atomically thin sheets have demonstrated promise as electrode materials due to their interlayer spacing allowing for easy lithium intercalation and diffusion. One family of such materials is the transition metal dichalcogenides (TMDCs) [2,3], which have already demonstrated promise in this application [4].<br/><br/>One particular material, SnS₂ has shown potential as an electrode material, demonstrating little volume change under lithiation [5]. Unfortunately, whilst this material has exhibited fast rates [6] and high capacities [7,8], this results in the consumption of the layered SnS₂ structure. Recent advances in CVD [9] have allowed the development of novel materials formed from the heterostructuring or superlatticing of component TMDCs. These ‘designed’ materials allow for tailoring of material properties by utilising the new physics that arises from their combination. Specifically, it provides the opportunity to optimise electronic transport, reduce lithium diffusion barriers, maintain the higher capacities that some structures offer, and could provide a new generation of electrode materials.<br/><br/>Using first principles density functional theory, we show how the properties of the SnS₂|TMDC heterostructures and superlattice systems can be predicted from the properties of the constituents, and how these new properties can be advantageous. We explain how the open-circuit voltage profiles and lithium diffusion barriers change for the composites, and the potential such structures have for future battery development. We then highlight a surprising improvement in the stability and storage capacity of certain pairs, which allow for further improvement of electrodes.<br/><br/>[1] Saxena, S et al . IEEE Industrial Electronics Magazine, 2017.<br/>[2] Lin, L et al . Energy Storage Materials, 2019, 19.<br/>[3] Chhowalla, M. et al. Nature Chemistry, 2013, 5.<br/>[4] Zhang, L et al. Nano Letters, 2018, 18, 1466-1475.<br/>[5] J. Morales, et al., Solid State Ionics, 1992, 51, 133.<br/>[6] B. Luo et al., Energy and Environmental Science, 2012, 5, 5226.<br/>[7] J. W. Seo et al., Advanced Materials, 2008, 20, 4269.<br/>[8] A. S. Hassan et al., Journal of Physical Chemistry C, 2016, 120, 2036.<br/>[9] Sherrell, P et al. ACS Appl. Energy Mater. 2019, 2, 8, 5877-5882.