Application of Ni-MOF derived Ni-C composite on separator modification for Li-S batteries

Abstract

In order to solve the problems caused by the low conductivity of sulfur and the shuttle effect of polysulfides in lithium-sulfur battery (LSB), we conducted a series of studies and successfully prepared Ni-C composite materials employing Ni-MOF as the precursor, which were used as coating materials for the separator of LSB. Two kinds of ligands, terephthalic acid and trimesic acid were used to react with nickel nitrate to obtain Ni-MOF precursors and their carbonized products were named as Ni-C(B) and Ni-C(T) respectively. Ni-MOF precursors with different morphologies were obtained by different ligands, the precursor of Ni-C(B) is the petal-like layered microspheres and the morphology maintained after calcination, the precursor of Ni-C(T) has the structure of drug flake and agglomerates into a massive structure during the reaction. Because of the uniform distribution of nickel particles and the advantages in morphology and specific surface area, the performance of batteries equipped with Ni-C(B) modified separator is better than that of Ni-C(T) sample. Through a series of electrochemical performance tests, the results are consistent with our expectations. When the sulfur area density in positive electrode is 3 mg cm⁻², the highest discharge capacity of the battery using Ni-C(B) coated separator is 1413.7 mAh g⁻¹ at 0.05C, 1169.7 mAh g⁻¹ at 0.1C and 997.3 mAh g⁻¹ at 0.3C. Furthermore, the initial discharge capacity is 926 mAh g⁻¹ at 0.5 C and can retain a capacity of 600 mAh g⁻¹ after 300 cycles.