Graphene nanocapsules improve Li-S battery electrodes

Researchers at the Argonne National Laboratory and Oregon State University in the U.S have designed a novel cathode architecture for lithium-sulphide batteries that consists of crystalline di-lithium sulphide nanoparticles encapsulated in few-layer graphene. The design is said to allow the maximum amount of active sulphur species to be incorporated into the electrode and so greatly improves its electrical conductivity. It also overcomes many of the major challenges associated with existing sulphur electrodes and di-lithium composites.

The Li₂S-graphene nanocapsules architecture can boast superior electrochemical properties. The electrodes have a high reversible capacity of 1160 mAh/g and area capacity of 8.1 mAh/cm2. The team synthesized the Li₂S@graphene nanocomposites in a one-step reaction in which they reacted lithium metal foils with CS₂ vapour carried by argon gas at 650°C. Li₂S nanocrystals and the tight wrapper of few-layer graphene are spontaneously generated, thus forming the nanocapsules. The Li₂ nanoparticles are between 50 and 80 nm in size and are uniformly and seamlessly encapsulated in about 10–20 graphene layers. This significantly reduces the charge-transfer resistance between the two materials and greatly improves the electric conductivity of Li2.