隨著化石燃料的頻繁使用，與之伴隨而來的溫室效應也日益加劇，造成極端氣候的產生。因此，持續尋找替代的永續能源可說是勢在必行，其中儲能材料－　鋰離子電池已廣泛應用，如智慧型手機、電腦、汽車等等。然而，鋰礦含量有限，將無法滿足未來市場需求，有鑑於此，與鋰金屬化學活性相似且含量高的鈉金屬受到了廣泛的關注。在鈉離子電池中，室溫鈉硫電池由於其理論容量高（1675 mAh g-1），材料成本低和地殼資源豐富而在近年來引起了可充電電池領域的高度研究。然而，硫的低電導率，容量衰減和穿梭效應是硫電池向應用發展的主要挑戰。
另外，由於提供硫的高利用率以及均勻分佈，在過去的幾十年中，在陰極中使用多硫化物作為活性材料是新的方向。但是，穿梭的多硫化物仍然限制了循環的穩定性。因此，非常需要改善循環能力的新型電催化劑。二硫化鉬是一種廣泛的二維材料，由於其高度活躍的極性邊緣位置而成為眾所周知的材料。在這方面，首先通過簡便的水熱法在碳布作為導電基質上合成了富邊緣位點的二硫化鉬。隨後，將由氨氣退火合成的二硫化鉬/氮化鉬異質結構作為電催化劑引入帶有陰極電解液的室溫鈉硫電池中，以促進多硫化物的轉換，降低穿梭效應所帶來的負面效果。還研究了電池測試中二硫化鉬和不同電解質鹽組成的電解液以及不同負載量的二硫化鉬在電池表現所帶來的影響。結果表明，通過在二硫化鉬中進行氮摻雜，可以獲得更穩定的循環和增強的庫倫效率，這表明二硫化鉬/氮化鉬異質結構可以作為鈉硫電池的有希望的電催化劑。

Room temperature sodium-sulfur (RT Na-S) batteries have attracted great attention in rechargeable batteries in recent years due to its high theoretical capacity (1675 mAh g-1), low material cost and abundant resources in the earth crust. However, the low electrical conductivity of sulfur, capacity-fading and shuttle effect are the major challenges in the development of sulfur batteries toward applications currently.
In addition, the use of high order polysulfides as the active material in the cathode is a new direction in the past few decades because of the homogeneous distribution supplying high utilization of sulfur. However, the shuttling high-order polysulfides still restricts the stability of the cycling. Therefore, a novel electrocatalyst improving cycling capability is highly needed. MoS2, a popular two-dimensional material, is well known material because of its highly active polar edge-sites. In this regard, the edge-site-rich MoS2 was first synthesized on the conductive matrix of carbon cloth by a facile hydrothermal process. Subsequently, a novel MoS2/MoN heterostructure synthesized by NH3 annealing was introduced as electrocatalyst in the RT Na-S batteries with catholyte to promote the evolution of polysulfides. The factors of different loading of MoS2 and electrolyte composed of variant electrolyte salts in Na-S battery tests were also investigated. The results show the more stable cycling and enhancement of columbic efficiency could be obtained by nitrogen doping in MoS2, suggesting that the MoS2/MoN heterostructure can be a promising candidate of electrocatalyst for Na-S batteries.

Table of Content
Abstract i
摘要 ii
致謝 iii
Table of Content iv
List of Figure Captions vi
Chapter 1 Introduction - 1 -
1.1 Li-S & Na-S batteries - 1 -
1.1.1 Overview of Li-S & Na-S batteries - 1 -
1.1.2 Shuttle Effect and Mechanism in Li-S & RT-Na/S batteries - 4 -
1.1.3 Strategies to avoid shuttle effect in Li-S & RT-Na/S batteries - 7 -
1.1.3.1 Sulfur/carbon composite cathode - 7 -
1.1.3.2 Interlayer - 8 -
1.1.4 Catholyte in Li-S & Na-S Batteries - 10 -
1.2 Electrocatalyst for Li-S & Na-S batteries - 12 -
1.2.1 Development of Electrocatalyst for Li-S & Na-S batteries - 12 -
1.2.2.1 Metal - 13 -
1.2.2.2 Oxides - 15 -
1.2.2.2 Nitrides - 17 -
1.2.2 Properties and Applications of MoS2 & MoN in Li-S batteries - 18 -
Chapter 2 Motivation - 22 -
Chapter 3 Material Synthesis and Characterization - 24 -
3.1 Synthesis Method of MoS2@CC, MoS2-MoN@CC and MoN@CC - 24 -
3.2 Preparation of sodium polysulfide catholyte - 25 -
3.3 Coin Cell Fabrication Process and Measurement - 25 -
3.4 Material Characterization - 26 -
Chapter 4 Results and Discussion - 27 -
4.1 Characterization of MoS2@CC, MoS2-MoN@CC, MoN@CC - 27 -
4.2 Performance of Na-S batteries with electrocatalyst - 35 -
4.3 Kinetic Studies of Na-S Battery with catalysts - 44 -
4.4 Ex-situ Characterization - 48 -
Chapter 5 Conclusion and Future perspectives - 52 -
Chapter 6 Reference - 53 -
 

1. Herbert, D.; Ulam, J., US Patent 3,043,896 (1962). 1962.
2. Ji, X.; Lee, K. T.; Nazar, L. F., A highly ordered nanostructured carbon-sulphur cathode for lithium-sulphur batteries. Nature materials 2009, 8, 500-6.
3. Kummer, J. T.; Weber, N., A sodium-sulfur secondary battery. Sae Transactions 1968, 76, 1003-1028.
4. Luo, X.; Wang, J.; Dooner, M.; Clarke, J., Overview of current development in electrical energy storage technologies and the application potential in power system operation. Applied Energy 2015, 137, 511-536.
5. Lu, X.; Kirby, B. W.; Xu, W.; Li, G.; Kim, J. Y.; Lemmon, J. P.; Sprenkle, V. L.; Yang, Z., Advanced intermediate-temperature Na–S battery. Energy Environ. Sci. 2013, 6, 299-306.
6. Li, T.; Xu, J.; Wang, C.; Wu, W.; Su, D.; Wang, G., The latest advances in the critical factors (positive electrode, electrolytes, separators) for sodium-sulfur battery. Journal of Alloys and Compounds 2019, 792, 797-817.
7. Byoung Ho Jeon, J. H. Y., Kwang Man Kim, In Jae Chung, Preparation and electrochemical properties of lithium-sulfur polymer batteries. Journal of Power Sources 2002, 109, 89-97.
8. Cheon, S.-E.; Choi, S.-S.; Han, J.-S.; Choi, Y.-S.; Jung, B.-H.; Lim, H. S., Capacity Fading Mechanisms on Cycling a High-Capacity Secondary Sulfur Cathode. Journal of The Electrochemical Society 2004, 151, A2067.
9. Peng, H.-J.; Huang, J.-Q.; Cheng, X.-B.; Zhang, Q., Review on High-Loading and High-Energy Lithium-Sulfur Batteries. Advanced Energy Materials 2017, 7, 1700260.
10. Wenzel, S.; Metelmann, H.; Raiß, C.; Dürr, A. K.; Janek, J.; Adelhelm, P., Thermodynamics and cell chemistry of room temperature sodium/sulfur cells with liquid and liquid/solid electrolyte. Journal of Power Sources 2013, 243, 758-765.
11. Pope, M. A.; Aksay, I. A., Structural Design of Cathodes for Li-S Batteries. Advanced Energy Materials 2015, 5, 1500124.
12. Yu, X.; Manthiram, A., Capacity Enhancement and Discharge Mechanisms of Room-Temperature Sodium-Sulfur Batteries. ChemElectroChem 2014, 1, 1275-1280.
13. Xin, S.; Yin, Y. X.; Guo, Y. G.; Wan, L. J., A high-energy room-temperature sodium-sulfur battery. Advanced materials 2014, 26, 1261-5.
14. Zhang, S. S., Liquid electrolyte lithium/sulfur battery: Fundamental chemistry, problems, and solutions. Journal of Power Sources 2013, 231, 153-162.
15. Wang, Y.-X.; Zhang, B.; Lai, W.; Xu, Y.; Chou, S.-L.; Liu, H.-K.; Dou, S.-X., Room-Temperature Sodium-Sulfur Batteries: A Comprehensive Review on Research Progress and Cell Chemistry. Advanced Energy Materials 2017, 7, 1602829.
16. Su, Y. S.; Manthiram, A., A new approach to improve cycle performance of rechargeable lithium-sulfur batteries by inserting a free-standing MWCNT interlayer. Chemical communications 2012, 48, 8817-9.
17. Yu, X.; Manthiram, A., Highly Reversible Room-Temperature Sulfur/Long-Chain Sodium Polysulfide Batteries. The journal of physical chemistry letters 2014, 5, 1943-7.
18. R. D. Rauh, K. M. A., G. F. Pearson, J. K. Surprenant, and S. B. Brummer, A Lithium-Dissolved Sulfur Battery with an Organic Electrolyte. J. Electrochem. Soc. 1979, 126, 523.
19. Zhang, S. S.; Read, J. A., A new direction for the performance improvement of rechargeable lithium/sulfur batteries. Journal of Power Sources 2012, 200, 77-82.
20. Xu, R.; Belharouak, I.; Li, J. C. M.; Zhang, X.; Bloom, I.; Bareño, J., Role of Polysulfides in Self-Healing Lithium-Sulfur Batteries. Advanced Energy Materials 2013, 3, 833-838.
21. Fu, Y.; Su, Y. S.; Manthiram, A., Highly reversible lithium/dissolved polysulfide batteries with carbon nanotube electrodes. Angewandte Chemie 2013, 52, 6930-5.
22. Yu, X.; Manthiram, A., Room-Temperature Sodium–Sulfur Batteries with Liquid-Phase Sodium Polysulfide Catholytes and Binder-Free Multiwall Carbon Nanotube Fabric Electrodes. The Journal of Physical Chemistry C 2014, 118, 22952-22959.
23. Babu, G.; Ababtain, K.; Ng, K. Y.; Arava, L. M., Electrocatalysis of lithium polysulfides: current collectors as electrodes in Li/S battery configuration. Scientific reports 2015, 5, 8763.
24. Al Salem, H.; Babu, G.; Rao, C. V.; Arava, L. M., Electrocatalytic Polysulfide Traps for Controlling Redox Shuttle Process of Li-S Batteries. Journal of the American Chemical Society 2015, 137, 11542-5.
25. Li, Y.-J.; Fan, J.-M.; Zheng, M.-S.; Dong, Q.-F., A novel synergistic composite with multi-functional effects for high-performance Li–S batteries. Energy & Environmental Science 2016, 9, 1998-2004.
26. Zhang, B. W.; Sheng, T.; Liu, Y. D.; Wang, Y. X.; Zhang, L.; Lai, W. H.; Wang, L.; Yang, J.; Gu, Q. F.; Chou, S. L.; Liu, H. K.; Dou, S. X., Atomic cobalt as an efficient electrocatalyst in sulfur cathodes for superior room-temperature sodium-sulfur batteries. Nature communications 2018, 9, 4082.
27. Liang, X.; Hart, C.; Pang, Q.; Garsuch, A.; Weiss, T.; Nazar, L. F., A highly efficient polysulfide mediator for lithium-sulfur batteries. Nature communications 2015, 6, 5682.
28. Kumar, A.; Ghosh, A.; Roy, A.; Panda, M. R.; Forsyth, M.; MacFarlane, D. R.; Mitra, S., High-energy density room temperature sodium-sulfur battery enabled by sodium polysulfide catholyte and carbon cloth current collector decorated with MnO2 nanoarrays. Energy Storage Materials 2019, 20, 196-202.
29. Dong, S.; Chen, X.; Zhang, X.; Cui, G., Nanostructured transition metal nitrides for energy storage and fuel cells. Coordination Chemistry Reviews 2013, 257, 1946-1956.
30. Das, B.; Reddy, M. V.; Rao, G. V. S.; Chowdari, B. V. R., Synthesis of porous-CoN nanoparticles and their application as a high capacity anode for lithium-ion batteries. Journal of Materials Chemistry 2012, 22, 17505.
31. Mosavati, N.; Salley, S. O.; Ng, K. Y. S., Characterization and electrochemical activities of nanostructured transition metal nitrides as cathode materials for lithium sulfur batteries. Journal of Power Sources 2017, 340, 210-216.
32. Sun, Z.; Zhang, J.; Yin, L.; Hu, G.; Fang, R.; Cheng, H. M.; Li, F., Conductive porous vanadium nitride/graphene composite as chemical anchor of polysulfides for lithium-sulfur batteries. Nature communications 2017, 8, 14627.
33. P. Raybaud, G. K., J. Hafner, H. Toulhoat, Ab initio density functional studies of transition-metal sulphides: I. Crystal structure and cohesive properties. J. Phys.: Condens. Matter 1997, 9, 11085.
34. Xie, J.; Zhang, H.; Li, S.; Wang, R.; Sun, X.; Zhou, M.; Zhou, J.; Lou, X. W.; Xie, Y., Defect-rich MoS2 ultrathin nanosheets with additional active edge sites for enhanced electrocatalytic hydrogen evolution. Advanced materials 2013, 25, 5807-13.
35. Zhou, Q.; Su, S.; Cheng, P.; Hu, X.; Gao, X.; Zhang, Z.; Liu, J.-M., Vertically conductive MoS2 pyramids with a high density of active edge sites for efficient hydrogen evolution. Journal of Materials Chemistry C 2020, 8, 3017-3022.
36. Radisavljevic, B.; Radenovic, A.; Brivio, J.; Giacometti, V.; Kis, A., Single-layer MoS2 transistors. Nature nanotechnology 2011, 6, 147-50.
37. Wang, H.; Zhang, Q.; Yao, H.; Liang, Z.; Lee, H. W.; Hsu, P. C.; Zheng, G.; Cui, Y., High electrochemical selectivity of edge versus terrace sites in two-dimensional layered MoS2 materials. Nano letters 2014, 14, 7138-44.
38. Babu, G.; Masurkar, N.; Al Salem, H.; Arava, L. M., Transition Metal Dichalcogenide Atomic Layers for Lithium Polysulfides Electrocatalysis. Journal of the American Chemical Society 2017, 139, 171-178.
39. He, J.; Hartmann, G.; Lee, M.; Hwang, G. S.; Chen, Y.; Manthiram, A., Freestanding 1T MoS2/graphene heterostructures as a highly efficient electrocatalyst for lithium polysulfides in Li–S batteries. Energy & Environmental Science 2019, 12, 344-350.
40. Chen, G.; Song, X.; Wang, S.; Chen, X.; Wang, H., Two-dimensional molybdenum nitride nanosheets modified Celgard separator with multifunction for Li S batteries. Journal of Power Sources 2018, 408, 58-64.
41. Rana, M.; Li, M.; He, Q.; Luo, B.; Wang, L.; Gentle, I.; Knibbe, R., Separator coatings as efficient physical and chemical hosts of polysulfides for high-sulfur-loaded rechargeable lithium–sulfur batteries. Journal of Energy Chemistry 2020, 44, 51-60.
42. Yu, M.; Zhou, S.; Wang, Z.; Wang, Y.; Zhang, N.; Wang, S.; Zhao, J.; Qiu, J., Accelerating polysulfide redox conversion on bifunctional electrocatalytic electrode for stable Li-S batteries. Energy Storage Materials 2019, 20, 98-107.
43. Zhang, N.; Gan, S.; Wu, T.; Ma, W.; Han, D.; Niu, L., Growth Control of MoS2 Nanosheets on Carbon Cloth for Maximum Active Edges Exposed: An Excellent Hydrogen Evolution 3D Cathode. ACS applied materials & interfaces 2015, 7, 12193-202.
44. Eng, A. Y. S.; Cheong, J. L.; Lee, S. S., Controlled synthesis of transition metal disulfides (MoS2 and WS2) on carbon fibers: Effects of phase and morphology toward lithium–sulfur battery performance. Applied Materials Today 2019, 16, 529-537.
45. Wang, T.; Sun, C.; Yang, M.; Zhao, G.; Wang, S.; Ma, F.; Zhang, L.; Shao, Y.; Wu, Y.; Huang, B.; Hao, X., Phase-transformation engineering in MoS 2 on carbon cloth as flexible binder-free anode for enhancing lithium storage. Journal of Alloys and Compounds 2017, 716, 112-118.
46. Zhang, B.; Cui, G.; Zhang, K.; Zhang, L.; Han, P.; Dong, S., Molybdenum nitride/nitrogen-doped graphene hybrid material for lithium storage in lithium ion batteries. Electrochimica Acta 2014, 150, 15-22.
47. Yu, H.; Zhu, C.; Zhang, K.; Chen, Y.; Li, C.; Gao, P.; Yang, P.; Ouyang, Q., Three-dimensional hierarchical MoS2 nanoflake array/carbon cloth as high-performance flexible lithium-ion battery anodes. J. Mater. Chem. A 2014, 2, 4551-4557.
48. Geng, C.; Buchholz, D.; Kim, G. T.; Carvalho, D. V.; Zhang, H.; Chagas, L. G.; Passerini, S., Influence of Salt Concentration on the Properties of Sodium‐Based Electrolytes. Small Methods 2018, 3, 1800208.
49. Huang, Y.; Zhao, L.; Li, L.; Xie, M.; Wu, F.; Chen, R., Electrolytes and Electrolyte/Electrode Interfaces in Sodium-Ion Batteries: From Scientific Research to Practical Application. Advanced materials 2019, 31, e1808393.
50. Xu, X.; Zhou, D.; Qin, X.; Lin, K.; Kang, F.; Li, B.; Shanmukaraj, D.; Rojo, T.; Armand, M.; Wang, G., A room-temperature sodium-sulfur battery with high capacity and stable cycling performance. Nature communications 2018, 9, 3870.
51. Li, H.; Zhang, Q.; Yap, C. C. R.; Tay, B. K.; Edwin, T. H. T.; Olivier, A.; Baillargeat, D., From Bulk to Monolayer MoS2: Evolution of Raman Scattering. Advanced Functional Materials 2012, 22, 1385-1390.
52. Bruce Dunn, H. K., Jean-Marie Tarascon, Electrical Energy Storage for the Grid : A Battery of Choices. Science 2011, 334, 928-935.
53. Wu, H. L.; Huff, L. A.; Gewirth, A. A., In situ Raman spectroscopy of sulfur speciation in lithium-sulfur batteries. ACS applied materials & interfaces 2015, 7, 1709-19.
54. Wei, S.; Xu, S.; Agrawral, A.; Choudhury, S.; Lu, Y.; Tu, Z.; Ma, L.; Archer, L. A., A stable room-temperature sodium-sulfur battery. Nature communications 2016, 7, 11722.
55. Huang, J.-Q. Z., T.-Z.; Zhang, Q.; Peng, H.-J.; Chen, C.M.; Wei, F., Permselective Graphene Oxide Membrane for Highly Stable and Anti-Self-Discharge Lithium–Sulfur Batteries. ACS Nano 2015, 9, 3002-3011.
56. Chung, S.-H.; Luo, L.; Manthiram, A., TiS2–Polysulfide Hybrid Cathode with High Sulfur Loading and Low Electrolyte Consumption for Lithium–Sulfur Batteries. ACS Energy Letters 2018, 3, 568-573.
57. Wang, L.; Chen, X.; Li, S.; Yang, J.; Sun, Y.; Peng, L.; Shan, B.; Xie, J., Effect of eutectic accelerator in selenium-doped sulfurized polyacrylonitrile for high performance room temperature sodium–sulfur batteries. Journal of Materials Chemistry A 2019, 7, 12732-12739.