▎ 摘　　要

NOVELTY - An electrochemical device has a cathode comprising graphene-wrapped lithium sulfide nanoparticles. The nanoparticles are prepared by heating lithium metal, and a carbon source and/or sulfur source in a sealed container at a temperature to produce lithium vapors, and vapors of carbon source and/or sulfur source, and cooling the sealed container. USE - Electrochemical device e.g. primary batteries, secondary batteries or capacitors used in portable electronic device e.g. laptop computer and cell phone. ADVANTAGE - The electrochemical device has improved safety due to the use of lithium disulfide cathode which prevents the dendrite growth and the redox shuttles of lithium polysulfides which lead to low coulombic efficiency. The graphene-wrapped lithium disulfide nanoparticles exhibit increased conductivity relative to lithium disulfide. The lithium disulfide battery has high capacity, high lithium sulfide loading and high coulombic efficiency. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following: (1) cathode; and (2) preparation of graphene-wrapped lithium disulfide nanoparticles.