Li2S encapsulated by nitrogen-doped carbon for lithium sulfur batteries

Abstract

Using high-energy ball milling of the Li₂S plus carbon black mixture followed by carbonization of pyrrole, we have established a facile approach to synthesize Li₂S-plus-C composite particles of average size ∼400 nm, encapsulated by a nitrogen-doped carbon shell. Such an engineered core–shell structure exhibits an ultrahigh initial discharge specific capacity (1029 mA h g⁻¹), reaching 88% of the theoretical capacity (1166 mA h g⁻¹ of Li₂S) and thus offering the highest utilization of Li₂S in the cathode among all of the reported works for the encapsulated Li₂S cathodes. This Li₂S/C composite core with a nitrogen-doped carbon shell can still retain 652 mA h g⁻¹ after prolonged 100 cycles. These superior properties are attributed to the nitrogen-doped carbon shell that can improve the conductivity to enhance the utilization of Li₂S in the cathode. Fine particle sizes and the presence of carbon black within the Li₂S core may also play a role in high utilization of Li₂S in the cathode.