Regulating the proximity of d-p band center in TiP₂O₇ by the crystalline-amorphous heterointerface to boost adsorption-catalysis for LiPSs in Li-S batteries

The adsorption-catalysis ability of metal-based catalysts toward lithium polysulfides (LiPSs) is dominated by the position of their d-/p-band center. An available strategy to strengthen the d-p band center proximity of metal-based catalysts is to fabricate a crystalline-amorphous heterointerface, which markedly enhances LiPS conversion. The polyanionic pyrophosphate of TiP₂O₇ serves as an efficient catalyst and ionic conductor for lithium-sulfur (Li-S) batteries. However, TiP₂O₇ does not fully optimize sulfur redox reactivity due to limitations in factors such as the adsorption-catalysis of sulfur species, Li⁺ diffusion, and electron transfer. Herein, we engineer the crystalline-amorphous heterointerface of TiP₂O₇ combined with carbon nanotubes (CNTs) to facilitate electronic donation from C to TiP₂O₇. This interaction results in an upward shift of the Ti d, enhancing the proximity of the d-p band center in TiP₂O₇/CNTs. By utilizing TiP₂O₇/CNTs as both electrode and separator modifier, we optimize the LiPS conversion process, showing a comprehensive strategy to mitigate the diffusion of LiPSs and achieve the bidirectional redox reactions in Li-S batteries. Accordingly, the cell assembled by TiP₂O₇/CNTs delivers a satisfactory capacity of 835 mAh g⁻¹ after 300 cycles at 4 C and an impressive initial areal capacity of 3.52 mAh cm⁻² under the sulfur areal loading of 5 mg cm⁻² at 0.1 C. Additionally, the Li//Li cells utilizing TiP₂O₇/CNTs present a prolonged cycling life of up to 1800 h without voltage fluctuation and Li dendrite growth.