A dual-functional interlayer for Li–S batteries using carbon fiber film cladded electron-deficient Li2B4O7

The electron-deficient property of the atoms in functional materials endow them with tunable adsorption and catalysis effects on polysulfides, thus improving the performance of lithium–sulfur batteries. In this work, Li2B4O7 nanoparticles, which have abundant electron deficiencies derived from the [BO3] Lewis acid units, were uniformly cladded in the carbon nanofibers (LBO–CNF) and employed as interlayers for Li–S batteries. This functionalized interlayer expressed a high adsorption energy of ∼3.6 eV for polysulfides (e.g., Li2S6 and Li2S4) and effectively suppressed the polysulfides' shuttle behavior, delivering a high reversible capacity of 1242.6 mA h g−1 at 0.2C and good cycling performance with a low fading rate of 0.068% per cycle at 1C, thus effectually inhibiting the phenomenon of self-discharge. Besides, the lithiation reaction kinetics was also effectively enhanced, enhancing the rate performance of the battery to 644 mA h g−1 at 5C. This work provides a new strategy to enhance the electrochemical performance of Li–S batteries by applying the compounds of electronic-deficiency B-species and functionalized carbon.