Using a Metal Oxide Nanoparticle Interlayer To Efficiently Anchor Polysulfides at High Mass Loading S‑Cathodes in Li–S Rechargeable Battery

The bulk of the work related to a Li–S rechargeable battery revolves around materials design strategies of a suitable carbon­(/noncarbon)–host matrix targeted toward the entrapment of sulfur and prevention of leaching out of polysulfides into the electrolyte. This strategy, however, limits the extent of sulfur loading and, depending on the host, may simultaneously increase the unutilizable mass of sulfur in the electrode. Recently, usage of interlayers between conventional S|C composite cathode and separator has been demonstrated in Li–S batteries. This interlayer, mostly carbon or doped carbon, has been used to trap the polysulfides in between the interlayer and S-cathode. Instead of carbon, we demonstrate here an alternative and novel interlayer of metal oxide nanoparticles between cathode and separator to efficiently trap and arrest the polysulfides at the S-cathode. Oxide-based compounds exhibit a superior ability to hold the lower order polysulfides toward the S-cathode by bonding interactions, thereby enhancing anode protection. We employ pseudocapacitive metal oxides viz. Ni­(OH)₂ and NiO as the interlayers for efficient anchoring of the polysulfide. In the presence of the Ni­(OH)₂/NiO nanoparticle interlayer, an alternative pathway for sulfur reduction and oxidation takes place which simultaneously leads to a phenomenal reduction in the polysulfide shuttle effect, even at extremely high loadings of sulfur (up to 15 mg cm^–2). The beneficial role of the interlayers in inhibiting the shuttle effect is studied via in depth ex situ UV–vis and powder X-ray diffraction of the battery separator and the interlayer, respectively, cycled at various depths of discharge and charge. The conventional Li–S cell with S/C composite cathodes and metal oxide interlayers exhibits a remarkable improvement in both cycliability and rate capability (range: C/10–5C) vis à vis the cell without any interlayer.