Chemisorption of polysulfides by keto groups modified Li4Ti5O12 nanofibers with 3D interwove network structure for LSBs

Abstract

Lithium-sulfur batteries (LSBs) possess high energy density but suffer from severe capacity fading due to the dissolution of lithium polysulfide (LiPSs). Novel design and mechanisms to encapsulate LiPSs are greatly desired by high-performance LSBs towards practical applications. Herein, we report a strategy of preparing Lithium titanate (Li4Ti5O12, LTO) nanofibers using bacterial cellulose as excellent biomimetic mineralization template at room temperature. Natural abundant organic molecule of Anthraquinone (AQ) combine with the zero strain fast ionic conductor of LTO can inhibit the dissolution and diffusion of LiPSs through redox reactions during cycling. The keto groups (C = O) of AQ play a critical role in forming strong Lewis acid-based chemical bonding. The 3D interwove network structure of LTO nanofibers also hinders the shuttle effect of LiPSs. Polydopamine (PDA) coated on the outermost layer not only improves the conductivity of the whole electrode, but also enhances the wettability of the electrolyte. The long-term stability of S-based electrode is ensured by the synergistic effect of the three. This mechanism leads to a long cycling stability of S-based electrodes. With a high sulfur content of ∼ 70%, a low capacity decay of 0.042%, 0.063% and 0.061% per cycle for 500 cycles at the current densities of 1, 2 and 4C, respectively. The water-soluble binder was adopted, which was a solid step for the practical application of LSBs. This finding and understanding paves an alternative avenue for the future design of S-based cathodes toward the practical application of LSBs.