Advanced Materials for High Performance Lithium-Sulfur Batteries

Date of Award


Degree Name

Doctor of Philosophy


Engineering and Applied Sciences

First Advisor

Qingliu Wu, Ph.D.

Second Advisor

Kecheng Li, Ph.D.

Third Advisor

Dewei Qi, Ph.D.

Fourth Advisor

Peter Aurora, Ph.D.


Biomass, carbon aerogel, catalyst, electrochemical, lithium battery, lithium sulfur battery


With the advantages of high capacity and low cost, lithium-sulfur batteries (LSBs) have been considered as one of the most promising candidates for next-generation batteries. However, the wide adoption of LSBs to the commercial markets is limited due to the fast capacity decay and low utilization of sulfur. To address these issues, advanced cathodes with high electronic conductivity and strong affinity to elemental sulfur and lithium polysulfides, which are intermediate products during the charge/discharge process, have been developed in this program. Carbon aerogels (RFCs) with controllable porous architectures have been fabricated through adjusting the process parameters and used as the host materials in the sulfur cathodes. The experimental results demonstrated that RFC produced at 900 C and ramp of 2 C/min (RFC942) has the highest porosity and volume ratio of large to small pores. This special structure provides not only strong affinity to trap polysulfides, but also channels for fast electrolyte transport, leading to the highest rate capability and longest cycle life. We then extended the achieved knowledge and experience on RFC-based cathodes to investigate biomass-derived carbon materials as hosts of sulfur cathodes. Carbons derived from garlic acid delivered a high reversible capacity of > 800 mAh/g and retain >80% of initial capacity after 200 cycles. The promising LSB performance can be ascribed to the unique porous architecture of biomass-derived carbons. This result is consistent with what we observed from RFC-based sulfur cathodes. Acting as the catalysts, metals and/or metal oxides (referred to be dopant, thereafter) have also been integrated into RFCs and used as host materials for sulfur cathodes. The effect of processing conditions on the performance of RFCs with catalysts was investigated. Among all catalysts studied here, the cathodes with Ni-based catalysts demonstrated the best electrochemical behaviors. For instance, RFC@NiOx demonstrated the high reversible capacity of ~1000 mAh/g at 0.1C and the high durability with >85% capacity retained after 175 cycles. The excellent performance of LSBs is ascribed to the high electrical conductivity of metallic Ni and strong catalytic effect of NiOx in the RFC@NiOx host. Cells with RFC@Ni demonstrated further improved specific energy and elongated cycle life. The significantly improved LSB performance is associated with the unique properties of RFC@Ni host, which trap the soluble polysulfides, accelerate the polysulfide interconversion and facilitate mass transport. In addition, an environment-friendly aqueous cellulose nanocrystal (CNC) was applied as binder in the sulfur cathodes. The experimental results showed that CNC has strong affinity to polysulfides through analogous hydrogen bonds. Further, CNC has the reinforcement effect on the mechanical strength of sulfur cathodes to accommodate large volume change and maintain high electronic connectivity.

In summary, we successfully developed an advanced sulfur cathode from advanced host material and binders. All these advanced sulfur cathodes show excellent electrochemical performance with high capacity and unprecedentedly long cycle life.

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