Strongly coupled interfaces between a heterogeneous carbon host and a sulfur-containing guest for highly stable lithium-sulfur batteries: Mechanistic insight into capacity degradation

The use of conductive frameworks as the host scaffold to obtain nanostructured sulfur cathodes is an efficient way to increase the sulfur utilization for redox reaction in Li-S batteries with large discharge capacity and high energy density. However, due to dynamical interfaces driven by phase evolution between the conductive hosts and S-containing guests during cycling, the cathode still faces poor stability. Herein, the use of O-/N-containing nanocarbon as the conductive host sheds a light on the role of the dynamic interface between the carbon host and S-containing guest for a stable Li-S cell. The outstanding reversibility and stability of N-doped C/S cathodes are attributed to the favorable guest-host interaction at the electron-modified interface, manifesting as (i) a chemical gradient to adsorb polar polysulfides and (ii) ameliorative deposition and recharging of Li₂S on the region of electron-rich pyridinic N and a graphene domain surrounding quaternary N. Highly reversible, efficient and stable Li storage properties such as mitigated polarization and charge barrier, high capacity of 1370 and 964 mAh g^-1 at 0.1 and 1.0 C, respectively, and 70% of capacity retention after 200 cycles are achieved. Mechanistic insight into the capacity fading inspires the rational design on electrodes for high-performance electrochemical systems. Strongly coupled interfaces between conductive hosts and sulfur-containing guests: A chemical gradient is built to adsorb polar polysulfides and allow facile deposition of recharged Li₂S by electron-rich pyridinic nitrogen and a carbon surface around the quaternary nitrogen. Therefore, the nitrogen-doped carbon nanotubes exhibit a remarkably improved lithium storage performance in lithium-sulfur batteries.