### 石墨烯包覆的硫填充碳纳米笼自支撑整体材料的制备及其锂硫电池性能研究

1. 南京大学化学化工学院 介观化学教育部重点实验室 南京 210023
• 投稿日期:2018-04-08 发布日期:2018-05-31
• 通讯作者: 吴强, 王喜章 E-mail:wqchem@nju.edu.cn;wangxzh@nju.edu.cn
• 基金资助:

国家重点研发计划（No.2017YFA0206500）、国家自然科学基金（Nos.21773111，21473089，51571110，21573107）、常州市科技计划（No.CE20130032）、江苏高校优势学科建设工程和中央高校基本科研业务费专项资金资助项目.

### Free-Standing Monolithic Sulfur Cathode of Reduced Graphene Oxide Wrapped Sulfur-Filled Carbon Nanocages with High Areal Capacity

Wang Xiao, Li Youbin, Du Lingyu, Gao Fujie, Wu Qiang, Yang Lijun, Chen Qiang, Wang Xizhang, Hu Zheng

1. Key Laboratory of Mesoscopic Chemistry of MOE, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023
• Received:2018-04-08 Published:2018-05-31
• Contact: 10.6023/A18040135 E-mail:wqchem@nju.edu.cn;wangxzh@nju.edu.cn
• Supported by:

Project supported by the National Key Research and Development Program of China (No. 2017YFA0206500), NSFC (Nos. 21773111, 21473089, 51571110, 21573107), the Changzhou Technology Support Program (No. CE20130032), the Priority Academic Program Development of Jiangsu Higher Education Institution, and Fundamental Research Funds for the Central Universities.

Lithium-sulfur (Li-S) batteries have attracted considerable attention due to their high theoretical energy density, low cost and low toxicity of active materials. Despite the great progress achieved recently, the practical application of Li-S batteries still faces several critical challenges, i.e, low capacities, low coulombic efficiency and rapid capacity decay during cycling. These problems mainly originate from the reasons of:(i) the poor intrinsic electrical conductivity of sulfur and Li2S decreasing the utilization of sulfur, (ii) the shuttle effect of soluble polysulfide intermediates losing active components, (iii) the large volumetric change pulverizing electrode during cycling, which become more and more serious when the sulfur loading is increased to the practical level of 3~5 mg·cm-2. To address these issues, some approaches have been developed, including hybridizing sulfur with highly conductive materials to enhance the conductivity, encapsulating sulfur in porous materials to inhibit the loss of polysulfides and accommodate the volumetric expansion, blending sulfur with polar materials to restrain the diffusion of polysulfides by chemical interaction. Recently, our group reported the mesostructured cathode material of sulfur-filled carbon nanocages (S@hCNC), which demonstrated the large capacity, high-rate capability and long cycle life owing to unique mesostructured feature, physical confinement, good conductivity and coexisting micro-meso-macropores. However, the non-polar sp2 carbons only have weak interaction with polar polysulfides. The introduction of chemical adsorption sites for polysulfides through heteroatom doping or surface modification can obviously enhance the interaction between the host and lithium polysulfides, thus further improving the cycling stability. Herein, we report the free-standing monolithic materials of reduced graphene oxide wrapped S@hCNC (S@hCNC@rGO), which can be directly used as the cathode without using binders, conductive materials and current collector. The S@hCNC@rGO battery with the high areal sulfur loading of 3.8 mg·cm-2 delivers excellent electrochemical performances surpassing the counterpart of S@hCNC, e.g., high reversible specific capacity (1104 mAh·g-1@0.2 A·g-1), superior cycle stability (low degradation rate of 0.049% per-cycle@1.0 A·g-1), high coulombic efficiency (>99.9%) and the top-ranking areal capacity of 3.7 mAh·cm-2. Such excellent electrochemical performances can be ascribed to the synergism of the physical confinement of hCNC, the chemical adsorption of oxygen functional groups on rGO, the accelerated charge transfer kinetics arising from the hierarchical porous structure and high electrical conductivity, and the free-standing structure with high stability. This study also suggests a simple and efficient method to develop sulfur cathode with high areal capacity, which pave a way for the practical application of Li-S batteries.