Interfacial band structure modulation at electron coupled heterojunction balances sulfur redox kinetics in Li–S batteries

초록

D-band theory guided catalyst design of transition metal oxides (TMOs) targeting frontier orbitals of polysulfides has emerged as a promising route to suppress the polysulfide shuttle in lithium-sulfur (Li–S) batteries. However, this strategy often entails a trade-off, enhancing the sulfur reduction reaction (SRR) while compromising the sulfur evolution reaction (SER), or vice versa, depending on the position of TMOs’ d-band centers. Herein, to develop a catalyst with a well-balanced electronic structure capable of optimizing both reactions, we focused on modulating TMOs d-band center. Our DFT calculations reveal that physicochemical anchoring between TMOs and carbon matrix can shift the TMOs d-band center toward the polysulfide p-band center, thereby moderating TMO-polysulfide binding, lowering the SER barrier, and retaining SRR activity through efficient d-p hybridization. Based on these theoretical calculations, we developed a rationally designed MnO@CNT catalyst via laser ablation, where MnO nanoparticles are physicochemically anchored onto carbon nanotubes (CNTs) to achieve balanced SRR/SER kinetics. This physicochemical anchoring modulates the electronic structure of MnO, thereby accelerating polysulfide conversion and directing Li2S deposition toward dispersed 3D particulates rather than passivating 2D films, effectively alleviating electrode passivation at the end-of-discharge state. Consequently, Li–S cell incorporating MnO@CNT catalyst exhibits enhanced rate capability and prolonged cycling stability.

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