| dc.description.abstract | Lithium-ion batteries are widely used in portable electronics, electrical vehicle, stational power grid and many other applications, owing to the high energy density, high power density and good cyclability. The rapidly increasing demand for advanced energy storage system has motivated the research community to deliver the next-generation battery system beyond the Li-ion batteries (LIB) because LIB have reached the theoretical limit of the power and energy density. Li-S batteries have a higher theoretical capacity based on sulfur (1675mAh/g) and a higher energy density (2567 Wh/kg), benefiting from the conversion-type cathode material compared to the intercalation-type of traditional Li-ion battery cathode. Besides better energy storage performances, the low-cost raw material (sulfur) makes Li-S batteries the very promising candidate beyond LIB system. LIB which requires expensive metals, such as cobalt, titanium, nickel. Introducing of polysulfide anchoring materials provided a potential solution to the practical application of lithium sulfur battery. However, the practical application of Li-S batteries is impeded by several drawbacks including insulating sulfur/polysulfides deposited on the surface of electrodes, polysulfide shuttle in electrolytes, volume expansion while charging and discharging, lithium dendrites. Carbonaceous material has been considered as a promising candidate for LSB scaffold attribute to the outstanding electrochemical stability, electrical conductivity and mechanical strength.
This research starts with improving the performance of lithium-sulfur battery by introducing functional sites on the CNT with mechano-chemical treatment. Combining with lithium-infused anode, the cell exhibited a strikingly high areal capacity as high as 13.3 mAh/cm² at an areal current density of 1.6 mAh/cm², and maintained at 11.0 mAh/cm². Furthermore, MnO₂ decorated CNT anode was proposed to alleviate lithium dendrite formation on the electrode surface. In-operando and DFT calculation has shown that lithiophilic particle embedded in the porous and conductive medium could effectively suppress the lithium dendrite formation. The functionalized anode shows outstanding accumulative capacity over 10,000 mAh²/cm², which considers both cycling lifetime and areal capacity, even with large Li plating/stripping capacity of 6 mAh/cm² for more than 1800 hours. Additionally, parameters of lithium sulfur battery are investigated with experiments and simulation. The thickness-dependent study shows that thickness need to be carefully selected to avoid polarization, especially on high c-rate. The limitation factors for thick electrode, with high loading and high c-rate are investigated. The findings provide a methodology to optimize the performance of rate-capability, cycling life, and loading of active material. | |
