Li2S encapsulated by nitrogen-doped carbon for lithium sulfur batteries

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 similar to 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 (1165 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.