Electrochemical Activation of Super-P Carbon for Lithium-Sulfur Battery Cathodes?.

NICOLAS HOFFMAN; M. ORTIZ; S. GOMEZ; VISINTIN A.

Santiago

Congreso; International Workshop of Lithium Industrial Minerals and Energy (IWLIME 2020).; 2020

International Workshop od Lithium Industrial Minerals and Energy (IWLIME 2020).

The progress on lithium-ion batteries is close to reaching its physical upper bounds, and thus different chemical systems must be used to achieve higher energy densities. Among the chemistries currently under research, the system based on the reaction between lithium and sulfur is closest to adoption, with several prototypes demonstrating the viability of this technology. Lithium-sulfur batteries, with a theoretical capacity of 2567 Wh/kg, are expected to reach a practical capacity of 500 Wh/kg, almost tripling the 200 Wh/kg that lithium-ion batteries deliver on average.However, several engineering challenges must be overcome first. During normal functioning of a lithium-sulfur cell with elemental sulfur cathodes, complex polysulfides are generated and diffuse to the anode, causing material loss and limiting the active anode area. Sulfur itself is also an insulant, and thus requires an additive to ensure electrical contact with the rest of the circuit. Said additive is most often carbon, which can be enhanced with polar moieties to boost the strength of its interaction with the polysulfides].In this work, super-P carbon was modified by mechanical milling at 800 rpm for 30 minutes in ammonium hydroxide. The resulting material was dried for 24 hours for use as a sulfur scaffold, which was brought into its pores through a melt-diffusion treatment at 155ºC for 12 hours. The electrochemical behavior of the resulting material as the active ingredient in a lithium-sulfur cathode was evaluated in CR-2032 cells with a polypropylene Celgard H2010 separator and a lithium anode, compared to unmodified carbon used as the active ingredient.The initial capacity of the modified material after 10 cycles was 470 mAhg-1 compared to 410 mAhg-1 for the unmodified carbon, while the capacities on the first couple cycles were both around 600 mAhg-1. This demonstrates that modifying carbon has improved its capacity retention.