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, restricting 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 heterojunction 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.