报告题目：Li Metal Anode Protection in Lithium-Sulfur Batteries

　　主讲嘉宾：张强  研究员（清华大学）

　　时　　间：11月29日（周二）14:00—16:00

　　地　　点：李薰楼468会议室

　　报告简介：

　　Li metal is considered as the “Holy Grail” of energy storage systems due to its extremely high theoretical specific capacity (3860 mAh g？1), low gravimetric density (0.59 g cm^？3), and lowest negative redox potential (？3.040 V vs. standard hydrogen electrode). The bright prospects give rise to worldwide interests in the metallic Li for the next generation energy storage systems, including highly considered rechargeable metallic Li batteries such as Li-O₂ and Li-sulfur (Li–S) batteries. However, the formation of Li dendrites induced by inhomogeneous distribution of current density on the Li metal anode and the concentration gradient of Li ions at the electrolyte/electrode interface is a crucial issue that hinders the practical demonstration of high-energy-density metallic Li batteries.

　　A unique nanostructured anode with Li metal distributed in fibrous Li7B6 matrix is proposed as a promising anode to prevent the dendrite growth. The nanostructured anode is with a large specific area, thus rendering a low current density on the Li metal anode. The dendrite growth is effectively inhibited via decreasing the growth velocity of Li deposits and then limiting the final size of deposited Li on the nanostructured matrix, thus leading to the dendrite-free morphology at macroscale. The concentration gradient of Li ions near the anode surface are sharply reduced, because the 3D Li₇B₆ fibrous structure provides quantities of free space to accommodate electrolyte.

　　To improve the Coulombic efficiency of Li depositing/dissolution, a dual-phase Li metal anode containing polysulfide-induced SEI and nanostructured graphene framework was investigated for Li-S batteries. Free-standing graphene foam provides several promising features as underneath layer for Li anode, including (1) relative larger surface area than 2D substrates to lower the real specific surface current density and the possibility of dendrite growth, (2) interconnected framework to support and recycle dead Li, and (3) good flexibility to sustain the volume fluctuation during repeated incorporation/extraction of Li. The synergy between the LiNO3 and polysulfides provides the feasibility to the formation of robust SEI in an ether-based electrolyte. The efficient in-situ formed SEI-coated graphene structure allows stable Li metal anode with the cycling Coulombic efficiency of ～97 % with high safety and efficiency performance, which is with a low resistance of 19.65 Ω (29.10 Ω for Cu foil based Li metal anode) and high ion conductivity of 5.42×10^-2 mS cm^-1 (2.33×10^-2 mS cm-1 for Cu foil based Li metal anode).

　　These results indicated that interfacial engineering of nanostructured electrode were a promising strategy to handle the intrinsic problems of Li metal anodes, thus shed a new light toward LMBs, such as Li-S and Li-O₂ batteries with high energy density.

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[2] X. B. Cheng, et al. ACS Nano 2015, 9, 6373.
[3] R. Zhang, et al. Adv Mater 2016, 28, 2155.
[4] X.B. Cheng, et al. Adv Mater 2016, 28, 2888.
[5] Zhao CZ, et al. Energy Storage Materials 2016, 3, 77.
[6] Cheng XB, et al. Advanced Science 2016, 3, 1500213.

　　主讲嘉宾简介：

　　张强，清华大学特聘研究员，RSC Adv副主编。

　　曾获得英国皇家学会牛顿学者、国家自然科学基金优秀青年基金、The 2012-2015 Excellence in Review Awards for CARBON、2015 most prolific reviewers for Adv. Mater.等奖励。

　　从事能源材料，尤其是金属锂、锂硫电池、电催化及三维石墨烯的研究。主持国家重点研发计划课题、自然科学基金、教育部博士点基金等项目。担任Nature Energy、Sci. Adv.、JACS、Adv. Mater.、Angew. Chem. Int. Ed. 等期刊特约审稿人或仲裁人。

　　以第一作者/通讯作者在Adv. Mater., Adv. Funct. Mater., Nature Commun., Sci. Adv., J. Am. Chem. Soc., Angew. Chem. Int. Ed., Energy Environ. Sci.等发表SCI收录论文100余篇，30篇为ESI高引用学术论文。所发论文引用8700余次，h因子为51。申请中国专利22项(15项已授权)，PCT国际专利2项。