Journal
ACS APPLIED MATERIALS & INTERFACES
Volume 6, Issue 14, Pages 10908-10916Publisher
AMER CHEMICAL SOC
DOI: 10.1021/am405025n
Keywords
lithium-sulfur cell; sulfur-functionalized porous carbons; isothermal titration calorimetry; sulfur cathode; enhance polysulfude affinity; mesoporous carbons
Funding
- ConvEne IGERT Program of the National Science Foundation [DGE 0801627]
- MRSEC Program of the NSF [DMR 1121053]
- NSF
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The Li-S system offers a tantalizing battery for electric vehicles and renewable energy storage due to its high theoretical capacity of 1675 mAh g(-1) and its employment of abundant and available materials. One major challenge in this system stems from the formation of soluble polysulfides during the reduction of S-8, the active cathode material, during discharge. The ability to deploy this system hinges on the ability to control the behavior of these polysulfides by containing them in the cathode and allowing for further redox. Here, we exploit the high surface areas and good electrical conductivity of mesoporous carbons (MC) to achieve high sulfur utilization while functionalizing the MC with sulfur (S-MC) in order to modify the surface chemistry and attract polysulfides to the carbon material. S-MC materials show enhanced capacity and cyclability trending as a function of sulfur functionality, specifically a 50% enhancement in discharge capacity is observed at high cycles (60-100 cycles). Impedance spectroscopy suggests that the S-MC materials exhibit a lower charge-transfer resistance compared with MC materials which allows for more efficient electrochemistry with species in solution at the cathode. Isothermal titration calorimetry shows that the change in surface chemistry from unfunctionalized to S-functionalized carbons results in an increased affinity of the polysulfide intermediates for the S MC materials, which is the likely cause for enhanced cyclability.
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