Despite the high theoretical specific energy of lithium-sulfur (Li-S) batteries, due to poor electronic and ion conductivity of sulfur, slow dissolution of lithium polysulfide (LiPS), and slow redox kinetics, rapid capacity decay, low Coulombic efficiency, and low utilization efficiency of sulfur still pose serious challenges for the practical application of lithium-sulfur batteries.


To address these issues, Arumugam Manthiram of the University of Texas at Austin recently reported using hydrophilic molybdenum borate nanoparticles (MoB) as an effective catalytic additive for sulfur positive electrodes to improve LiPS conversion rate.


Key points of the article


1) MoB was prepared through a simple solid-state reaction. In short, fully mix anhydrous molybdenum chloride (MoCl5), boron (B) and tin (Sn), press them into particles, and then seal them in a quartz ampoule bottle. After heat treatment and acid treatment, dark gray MoB was obtained. TEM images indicate that the size of the synthesized MoB nanoparticles is within 15 nm. The HRTEM image shows α- The high crystallinity of MoB, with a lattice spacing of 0.27 nm, corresponds to α- The (103) side of MoB.


2) The high conductivity and abundant catalytic activity centers of MoB nanoparticles enable LIPS to exhibit rapid redox kinetics on a high sulfur loaded electrode (6.1 mg cm-2). In addition, the hydrophilicity and good wettability of MoB to electrolytes can promote electrolyte penetration and LiPS redox, ensuring high sulfur utilization under dilute electrolyte conditions.


3) The results showed that lithium sulfur batteries with MoB additives achieved impressive electrochemical performance, including high capacity (1253 mA h g-1) and ultra long lifespan (1000 cycles), with a capacity decay rate of only 0.03% per cycle. In addition, the soft pack battery manufactured with MoB additive has an ultra-high discharge capacity of 947 mA h g-1, corresponding to a low electrolyte capacity ratio of approximately 4.8 µ L (mA h) -1, and remains stable over 55 cycles under practical application conditions, with the electrolyte to sulfur ratio as low as 4.5 µ L mg-1.