高硫負載量是目前能夠實現高能量密度鋰硫電池的重要研究方向。但是，高硫負載量不可避免的會造成硫正極的厚度增加，從而產生低體積電容量的新挑戰。本研究，我們成功以簡易的一步合成法，製作出一種自支撐可撓性磷硫化合物混石墨烯的複合材料，它可以很容易的輾壓並製成小薄片，並可以直接用做新穎的高密度（1.8 g cm-3）硫正極。此材料硫單位面積含量高達6〜10 mg cm-2且硫含量為80％的正極，在電化學測試下，不僅具有優異的循環性能（在200次循環中硫的利用率為57％，每次循環容量衰減率為0.15％），而且還提供了克電量（959 mA h g 1）和面電量（5.5 mA h cm-2）。此外，根據近年相關高負載量的文獻，體積電容量（1901 mA h cm-3）是目前所見之最高紀錄。

High sulfur loading is a currently significant research to achieve the high energy density lithium sulfur battery. However, the high sulfur loading leads to increase the thickness of sulfur cathode creating the new challenge of low volumetric capacity. Here, we report a simple synthesis of self-supported flexible phosphorus-sulfur/graphene composites (PS/G composites), which can be easily pressed into sheet and can use directly as novel high dense (1.8 g cm-3) sulfur cathode. The cathode with high sulfur loading of 6 ~ 10 mg cm-2 and sulfur content of 80% not only delivers great stability cycling performance (57% of sulfur utilization and capacity fading rate 0.15%/cycle within 200 cycles), but also provides a excellent specific (959 mA h g-1) and areal (5.5 mA h cm-2) capacities. Remarkably, the corresponding volumetric capacity (1901 mA h cm-3) present the highest volumetric capacity, which is record high based on recently report, revealing a great potential for high energy density flexible lithium-sulfur battery.

Table of contents
Abstract--------------------------------------------------I
中文摘要 -----------------------------------------------II
Table of contents-----------------------------------------III
List of Figure--------------------------------------------IV
List of Tables--------------------------------------------V
Chapter 1. Introduction -------------------------------1
Development of Lithium-sulfur batteries-------------------1
Lithium-sulfur batteries : challenges---------------------4
The effect of electrolyte in Li-S batteries---------------8
Phosphorus sulfide molecules materials as sulfur cathode--12
Chapter 2. Experimental Section---------------------------14
Materials-------------------------------------------------14
Preparation of PS compounds-------------------------------14
Preparation of PS/G composites----------------------------14
Material Characterization---------------------------------15
Electrochemical characterization--------------------------15
Chapter 3. Result and discussion--------------------------16
Chapter 4. Conclusion-------------------------------------29
Reference-------------------------------------------------30

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