Phase and Orbital Engineering Effectuating Efficient Adsorption and Catalysis toward High-Energy Lithium-Sulfur Batteries.

Abstract

The delicate construction of electrocatalysts with high catalytic activity is a strategic method to enhance the kinetics of lithium-sulfur batteries (LSBs). Adjusting the local structure of the catalyst is always crucial for understanding the structure-activity relationship between atomic structure and catalyst performance. Here, in situ induction of electron-deficient B enables phase engineering Mo₂C, realizing the transition from hexagonal (h-Mo₂C) to cubic phase (c-B-Mo₂C). Meanwhile, the empty sp³ orbital of B favors the effective bonding with electron-rich sulfur, creates a more valid orbital engineering available. Relying on the binary engineering via B doping, the adsorption and conversion of polysulfides are promoted. Hence, the c-B-Mo₂C based cell achieves a low-capacity degradation of 0.04% with the coulombic efficiency exceeding 99.8% in 1000 cycles. Uniform Li⁺ transport is consistently achieved at 2 mA cm^-2 for over 600 h. A 6.67Ah-c-B-Mo₂C based pouch cell has a high energy density of up to 502.1 Wh kg^-1 (E/S ratio of 2.4 µL mg _S ^-1), while the pouch cell of 2 Ah exhibits an energy density of 372 Wh kg^-1 more than 100 cycles. This study takes advantage of the combined engineering method to provide a guiding approach for elevating the activity of the electrocatalysts rationally.