Guangtao Cong

Editorial: Functional units of nanocrystals: Synthesis, tailoring, and applications

Rationally-designed nitrogen-doped carbon-coated Co₉S₈–Co_1−xS yolk–shell hollow spheres are synthesized to buffer the volume fluctuation and enhance the electrical/ionic conductivity.

An easy and facile hydrothermal method is presented to synthesize hybrid materials of hollow mesoporous Zn _0.76 Co _0.24 S nanospheres anchored on reduced graphene oxide (rGO) sheets (Zn _0.76 Co _0.24 S@N/S-rGO), in which the obtained Zn _0.76 Co _0.24 S nanospheres are composed of numerous nanoparticles. Being evaluated as anode materials for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs), the Zn _0.76 Co _0.24 S@N/S-rGO composites exhibited a high reversible capacity of 804 and 605 mA h g ⁻¹ at the current density of 1 A g ⁻¹ after 500 cycles for LIBs and SIBs, respectively. The excellent electrochemical performance of Zn _0.76 Co _0.24 S@N/S-rGO composites originates from the synergistic effect between hollow Zn _0.76 Co _0.24 S nanospheres and reduction graphene, as well as the void spaces between the neighbouring nanoparticles of Zn _0.76 Co _0.24 S providing large contact areas with electrolyte and buffer zone to accommodate the volume variation during the cycling process.

Alkali metal–oxygen batteries promise high gravimetric energy densities but suffer from low rate capability, poor cycle life and safety hazards associated with metal anodes. Here we describe a safe, high-rate and long-life oxygen battery that exploits a potassium biphenyl complex anode and a dimethylsulfoxide-mediated potassium superoxide cathode. The proposed potassium biphenyl complex–oxygen battery exhibits an unprecedented cycle life (3,000 cycles) with a superior average coulombic efficiency of more than 99.84% at a high current density of 4.0 mA cm⁻². We further reduce the redox potential of biphenyl by adding the electron-donating methyl group to the benzene ring, which successfully achieved a redox potential of 0.14 V versus K/K⁺. This demonstrates the direction and opportunities to further improve the cell voltage and energy density of the alkali-metal organic–oxygen batteries.