3D Conductive Nanostructure with the Lewis Acid–Base Interaction for High-Performance Lithium–Sulfur Batteries

Abstract

Lithium–sulfur batteries have become glamorous candidates benefitting from their attractive specific capacity (1675 mAh g^–1) and nontoxic properties, but the existing problems remain to be solved. In this work, CoSe₂–nitrogen-doped carbon (CSN) connected by carbon nanotubes was synthesized with Prussian blue and melamine as a precursor and carbon source, respectively, and named as CSNC, which has high electronic conductivity and anchoring effect on lithium polysulfides (LiPSs). CSNC is used as both a sulfur carrier and a separator modification material. Furthermore, the stable CSNC framework slows down the volume change during the operation of the batteries. Electrochemical impedance spectroscopy and the Randles–Sevcik equation calculation verify that CSNC promotes the transformation reaction kinetics of LiPSs, and the UV–vis absorption spectrum confirms the effective adsorption of CSNC for LiPSs, accordingly inhibiting the shuttle effect. Because of the above advantages, lithium–sulfur battery with CSNC/S + CSNC/PP achieves a discharge capacity of 1056 mAh g^–1 at 0.5 C and a capacity retention of 85.5% over 100 cycles. The capacity retention rate of 79% is acquired under 1 C after 350 cycles. Good electrochemical performance is also obtained even under a low E/S of 4 μL mg^–1 and a high loading of 4.2 mg cm^–2. This research puts forward the further thinking on the direction of dual modification for both the cathode and separator, which would also be used in the field of other secondary batteries.