Lithium-sulfur (Li-S) batteries are regarded as a promising substitute to the current lithium-ion batteries. They have high energy density, five times higher than that of the state-of-the-art lithium-ion batteries, as well as the advantages of environmental benignity and low cost. 

However, the electrochemical performances of Li-S batteries are seriously compromised by the polysulfide (LiPS) shuttling during charge and discharge process. The LiPS dissolves into the electrolyte, causing a loss of active materials, and thus a decay of cycle performance for Li-S batteries. 

To solve the problems above, the Advanced Energy Storage Materials and Technology Group from the Qingdao Institute of Bioenergy and Bioprocess Technology (QIBEBT) of the Chinese Academy of Sciences (CAS) developed a novel nanocomposite for the modified separator of Li-S batteries.  

They used transition metal compound CoNi_1/3Fe₂O₄ (CNFO) nanoparticles and carbon nanotubes (CNT) as functional interlayer. Benefiting from the strong adsorption of CNFO and high conductivity of CNT, the Li-S batteries exhibited an excellent discharge capacity as high as 897 mAh g^-1 at 2.0 C and maintained 84% after 250 cycles.  

Meanwhile, a reversible specific capacity of 869 mAh g^-1 at 0.5 C with high Coulombic efficiency could be also obtained over 100 cycles at an elevated temperature (60 °C). The functional interlayer greatly inhibited the LiPS shuttling and boosted the electrochemical performance of Li–S batteries.  

The relevant work was published in ACS Applied Materials & Interfaces, and it was supported by the National Natural Science Foundation of China as well as the Dalian Institute of Chemical Physics & QIBEBT of CAS. 

Figure 1 (a) Schematic illustration of CNFO@CNT nanocomposite preparation. (b) UV-vis spectra of CNFO@CNT nanocomposite. (c) Cycle performance of Li-S batteries under 60°C. (Image by LIU Tao)