Heterostructured nickel-cobalt metal alloy and metal oxide nanoparticles as a polysulfide mediator for stable lithium-sulfur full batteries with lean electrolyte

Abstract

Batteries that utilize low-cost elemental sulfur and light metallic lithium as electrodes have great potential in achieving high energy density. However, building a lithium-sulfur (Li-S) full battery by controlling the electrolyte volume generally produces low practical energy because of the limited electrochemical Li-S redox. Herein, the high energy/high performance of a Li-S full battery with practical sulfur loading and minimum electrolyte volume is reported. A unique hybrid architecture configured with Ni-Co metal alloy (NiCo) and metal oxide (NiCoO2) nanoparticles heterogeneously anchored in carbon nanotube-embedded self-standing carbon matrix is fabricated as a host for sulfur. This work demonstrates the considerable improvement that the hybrid structure's high conductivity and satisfactory porosity promote the transport of electrons and lithium ions in Li-S batteries. Through experimental and theoretical validations, the function of NiCo and NiCoO2 nanoparticles as an efficient polysulfide mediator is established. These particles afford polysulfide anchoring and catalytic sites for Li-S redox reaction, thus improving the redox conversion reversibility. Even at high sulfur loading, the nanostructured Ni-Co metal alloy and metal oxide enable to have stable cycling performance under lean electrolyte conditions both in half-cell and full-cell batteries using a graphite anode.