Synthesis of Titanium Molybdenum Nitride-Decorated Electrospun Carbon Nanofiber Membranes as Interlayers to Suppress Polysulfide Shuttling in Lithium–Sulfur Batteries

The practical application of lithium–sulfur (Li–S) batteries is seriously restricted by the “shuttle effect” of polysulfide ions. The design of functional interlayers is one of the effective solutions to overcome this defect. In this work, titanium molybdenum nitride (TMN) solid solution nanoparticles have been successfully decorated on electrospun carbon nanofibers (CNFs) to form a continuous flexible TMN@CNF membrane through a one-step calcination process under NH3 atmosphere. By regulating the mass ratio of titanium acetylacetonate TiO(acac)2 and molybdenum acetylacetonate MoO2(acac)2, the dissolved amount of Mo into TiN can be precisely controlled. Through the visible adsorption test, cyclic voltammetry test of Li2S6-based symmetric cells, and potentiostatic discharge measurement, such a TMN@CNF membrane has been confirmed to exhibit excellent adsorption and catalytic capacity on lithium polysulfides. With the help of DFT calculations, the adsorption capacity of TMN phase is confirmed to be greatly enhanced when compared with that of TiN, which can be attributed to the improved overlap of the electronic state after the introduction of Mo to TiN. By using such a membrane as the interlayer in Li–S batteries, it can effectively increase the cell’s initial capacity to 1205 mA h g–1 at 0.5 C when the dissolved amount of Mo reaches 50%. At the current density of 2 C, the discharge capacity of the cell by using such a multifunctional interlayer can reach up to 947 mA h g–1 and remains at 390 mA h g–1 after 1000 cycles, corresponding to a 0.059% capacity decay per cycle. This work provides a feasible method to prepare a flexible interlayer with a regulated electronic fine structure and strong chemisorption and catalytic ability for the development of the high performance Li–S batteries.