ORALS

SESSION: BatteryMonPM3-R9	5th Intl. Symp. on Sustainable Secondary Battery Manufacturing and Recycling
Mon Nov, 5 2018 / Room: Asian (60/3rd)
Session Chairs: Hee-Dae Lim; Session Monitor: TBA

18:05: [BatteryMonPM314]
New Approaches in the Development of Advanced Lithium-sulfur Batteries
Jiazhao Wang¹ ; Xin Liang¹ ; Mohammed Rejaul Kaiser¹ ; Fang Li¹ ; Huakun Liu¹ ; ¹Institute for Superconducting and Electronic Materials, University of Wollongong, Wollongong, Australia;
Paper Id: 82 [Abstract]

Lithium Sulfur (Li-S) batteries are one of the most promising next generation battery technologies due to their high theoretical energy density, low materials cost, environmental friendliness, and relative safety [1]. Nevertheless, sulfur is an electrically insulating material, which leads to poor electrochemical accessibility and low utilization in the electrode. The polysulfide anions that are generated during cycling are highly soluble in the organic electrolyte solvent. The diffusion of polysulfides to the lithium anode results in low active material utilization, low Coulombic efficiency, and short cycle life of the sulfur electrode. In terms of making the lithium/sulfur batteries suitable for operation, carbon and conducting polymers are the promising conducting material to improving performance. Ternary composites with porous sulfur/dual-carbon architectures were synthesized by a single-step spray-pyrolysis/sublimation technique, which is an industry-oriented method that features continuous fabrication of products with highly developed porous structures [2]. A double suspension of commercial sulfur and carbon scaffolding particles was dispersed in ethanol/water solution and sprayed at 180°C using a spray pyrolysis system. In the resultant composites, the sulfur particles were subjected to an ultrashort sublimation process, leading to the development of a highly porous surface, and were meanwhile coated with amorphous carbon, obtained through the pyrolysis of the ethanol, which acts as an adhesive interface to bind together the porous sulfur with the scaffolding carbon particles, to form a ternary composite architecture. This material has an effective conducting-carbon/ sulfur-based matrix and interconnected open pores to reduce the diffusion paths of lithium ions, buffer the sulfur volumetric expansion, and absorb electrolyte and polysulfides. Because of the unique structure, the composites show stable cycling performance for 200 cycles and good rate capability of 520 mAh g-1 at 2°C. This advanced spray-pyrolysis/sublimation method is easy to scale up and shows great potential for the commercialization of Li-S batteries. Sulfur-conducting polymer composites were also investigated to improve the performance of Li-S batteries. A PPy@S@PPy composite with a novel three-layer-3D-structure was synthesised by the oxidative chemical polymerization method and chemical precipitation method. The discharge specific capacity of the PPy@S@PPy composite cathode is 554 mAh g-1 after 50 cycles, representing approximately 68.8% retention of the initial discharge specific capacity of about 801 mAh g-1 [3]. A free-standing sulfur-PPy cathode and a PPy nanofiber coated separator were designed for flexible Li-S batteries. The as-prepared PPy film not only has a rough surface, which can enhance adhesion of the active materials and trap dissolved polysulfides, but also possesses elastic properties, which can accommodate the volume expansion and maintain the integrity of electrode during cycling. On the other hand, the PPy-separator not only acts as a reservoir for soluble lithium polysulfides, but also acts as an upper current collector to accelerate the kinetics of the electrochemical reactions. Moreover, PPy is electrochemically active and could contribute to the capacity of Li-S batteries. Benefiting from the advantages above, the flexible Li-S battery can deliver an initial discharge capacity of 1064 mA h g-1, and retain a capacity of 848 mA h g-1 after 20 cycles at 0.1 C. After repeated bending of 10 times, the capacity remains almost the same. In addition, the soft-packaged Li-S battery could power a device containing 24 white LEDs, both before and after bending, indicating its great potential application in flexible electronics. We believe that this flexible electrode structure may provide guidance for fabricating high energy, flexible electrochemical energy-storage devices [4].

References:
[1] M. R. Kaise, S. L. Chou, H. K. Liu, S. X. Dou, C. S Wang, J. Z. Wang, Adv. Mater., 29 (2017) 1700449.
[2] X. Liang, M.R. Kaiser, K. Konstantinov, R. Tandiono, Z. Wang, C. Chen, H..K. Liu, S. X. Dou, and J. Z. Wang, ACS Appl. Mater. Interfaces, 8 (2016) 25251.
[3] X. Liang, M. Zhang, M. R. Kaiser, X. W. Gao, K. Konstantinov, R. Tandiono, Z. X. Wang, H. K. Liu, S. X. Dou and J. Z. Wang, Nano Energy, 11 (2015) 587.
[4] F. Li, M. R. Kaiser, J. Ma, Z. P. Guo, Z., H. K. Liu, J. Z. Wang, Energy Storage Materials, 13 (2018) 312.