Construction of Ti4O7/TiN/carbon microdisk sulfur host with strong polar N-Ti-O bond for ultralong life lithium-sulfur battery

As the desired sulfur host of lithium-sulfur battery, the strong polarity and fast electron migration capability are indispensable for achieving effective adsorption and conversion of lithium polysulfides (LiPSs), that is, restrict-ing the shuttle effect. Herein a porous microdisk Ti4O7/TiN/C heterojunction with strong polar N-Ti-O covalent bonds is precisely constructed. Compared with O-Ti-O or N-Ti-N bond in single Ti4O7 or TiN, the N-Ti-O bond with stronger polarity could adsorb and bond with S and Li atoms in LiPSs, which is beneficial for LiPSs adsorption. Beside, the Ti4O7/TiN heterostructure favors the electron transfer, which could promote the conversion of LiPSs. The design strategy is to construct abundant polar N-Ti-O bonds at Ti4O7/TiN heterogeneous interface that would realize the associative process of LiPSs adsorption, trapping, and conversion, thereby restraining the shuttle effect efficiently. In the current study, as the host of the sulfur cathode, the porous microdisk TiN/Ti4O7 /C heterojunc-tion exhibits a high specific capacity of 1204.5 mAh g(-1) at 0.2 C, and a high specific capacity of 616.5 mAh g(-1) at an ultrahigh current density of 4 C. In addition, 86.4% and 116.9% capacity are retained over 1000 cycles at 1 C and 2 C, respectively. This strategy provides an insight into developing lithium-sulfur battery with extraordinary performance, and opens promising routes to design the next-generation electrochemical energy storage devices.

Automated summary

The study focuses on constructing a porous microdisk Ti4O7/TiN/C heterojunction with strong polar N-Ti-O covalent bonds at the interface, which helps achieve effective adsorption and conversion of LiPSs, thus efficiently restraining the shuttle effect. The design strategy shows outstanding specific capacity and cycling retention at different current densities.