Rechargeable aluminum batteries (RABs) are amongst the most promising post-lithium energy storage systems (ESS) with a substantially higher specific volumetric capacity (8046 mA h cm−3), higher safety and lower cost.
has substantially increased. [1] Accordingly, lithium-sulfur batteries (LSBs) have gained much attraction as future-generation rechargeable batteries due to the exceptional-specific energy density of 2600 Wh kg −1 and theoretical-specific capacity of 1675 mAh g −1 , which are significantly higher than those of the traditional lithium-ion batteries. [2] Regardless of the great potential, LSBs face some great challenges that hinder their commercialization. Some of the major challenges are the low active material utilization, which is a consequence of the insulating nature of orthorhombic sulfur and its discharged products, volume expansion during redox reactions, and shuttle effect that occurs due to dissolution of long-chain lithium polysulfides (Li 2 S x , 4 ≤ x ≤ 8) into the electrolyte, allowing the formation of insoluble, insulating Li 2 S 2 /Li 2 S precipitates on the surface of lithium anode and sulfur cathode. The dissolution of polysulfides not only retards the reaction kinetics of the electrodes, but also causes low Coulombic efficiency, rapid capacity fading, and poor cycle life of the LSBs. [3] Meanwhile, the lithium is highly reactive and the gas generation during cycling also results in speedy capacity degradation of LSBs. [4] Lithium-sulfur batteries (LSBs) have been regarded as the supreme feasible future generation energy storage system for high-energy applications due to the exceptional-specific energy density of 2600 Wh kg −1 and theoretical-specific capacity of 1675 mAh g −1 . Nevertheless, some key challenges which are linked with polysulfide shuttling and sluggish kinetics of polysulfide conversion are the main obstacles in the high electrochemical performance of LSBs. Here, a molybdenum trioxide (MoO 3 ) nanobelt catalytic layer is fabricated on the separator to solve these issues. The MoO 3 layer shows strong chemical interaction with polysulfides by successfully blocking the polysulfides on the separator from shuttling and significantly accelerates the redox reaction of polysulfide conversion. Furthermore, the randomly arranged layers of MoO 3 nanobelts possess enough porous networks that provide effective space for electrolyte infiltration and facile pathway for fast ion transportation. The resultant LSBs exhibit a very high initial capacity of 1377 mAh g −1 . After 200 cycles at 0.5 C, the capacity is 684.4 mAh g −1 with the fading rate of only 0.251% per cycle. Additionally, the MoO 3 modification provides good surface protection of lithium anode and depresses the lithium anode degradation.
Battery Performance
The significant challenge in exploring novel nanostructured sulfur host materials for Li‐S batteries is to simultaneously mitigate the notorious shuttle effect and catalytically enhance the redox kinetics of lithium polysulfides (LPSs). Herein, a novel ultrafine Mo2C nanoparticles uniformly distributed on 2D nanosheet‐assembled 3D hollow nitrogen‐doped carbon flowers (HNCFs) is designed. The Mo2C/HNCFs architecture with unique flower‐like morphologies not only efficiently suppressed the aggregation of 2D nanosheets but also highly distributed the ultrafine Mo2C nanoparticles that act as catalytic active sites for efficient adsorption and conversion of LPSs. Furthermore, the 3D hierarchical arrangement can afford ample internal space to accommodate sulfur species, large volume expansion, 3D electron pathway, and physical/chemical blockage of LPSs to reduce the loss of active materials. The Mo2C/HNCFs composite exhibits a high rate capability, unprecedented capacity retention of 92% over 100 cycles at 0.5 C placing Mo2C/HNCFs one of the best LPSs adsorbents and electrocatalysts.
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