锂在单层石墨烯表面异相成核研究及理想碳基骨架的构建

Recently, growing research efforts have been devoted to constructing a stable and efficient Li metal anode for next-generation batteries with high energy density such as Li-S batteries. There has been significant progress in stabilizing Li anode, including Li metal alloying, optimizing electrolyte components, et al; however, structural Li metal anode maybe the only one route to tackle dendrite growth as well as infinite relative volume change for electrode materials, of which the carbon-based skeleton materials is promising to control Li deposition. However, there have been few studies done on fundamental understanding of heterogeneous nucleation and growth for Li metal deposition on carbon materials, and the carbon frame materials used and corresponding construction of electrodes still remain at trial-and-error stage, largely hindering the development of Li metal anode. Here we will explore the nucleation pattern of lithium on single-crystalline and polycrystalline graphene growing on super flat copper substrates both in ether-based and ester-based electrolytes, and then unravel the effect of graphene grain boundaries and oxygen/nitrogen atom doping on the electrodeposition of lithium atoms. On this basis, the optimized porous single-layer graphene will be applied to construct three-dimensional mesoporous carbon skeleton, and three relationships including the rich lithium-active sites reducing the overpotential of lithium deposition, the capillary action from developed mesoporous structure improving the surface lithiophilic ability, and the confinement effect influencing the morphology of lithium deposition, will be studied. We hope to raise the strategy for designing a stable and efficient Li metal anode based on these results.

如何构筑稳定高效的金属锂负极是锂硫电池等下一代高比能电池的研究热点。研究者探索了锂合金化、电解液添加剂等多种稳定化方法，但只有结构化锂负极的策略有望同时解决锂枝晶生长和电极体积变化的问题。近期研究结果表明，碳骨架金属锂负极前景较好，然而，目前关于锂在碳上的异相成核与生长的基础研究仍是空白，碳骨架的选择与电极构建仍处于经验性试错阶段，阻碍了金属锂负极的发展。在前期工作基础上，本课题提出以超平铜箔上生长的单层石墨烯单晶和多晶直接作为载体电极，研究醚类和酯类电液中锂在其上电沉积成核与生长的规律，结合理论模拟阐明碳晶格上晶界拓扑缺陷、氧／氮掺杂等电子结构性质对锂沉积行为的影响。在此基础上，以优化的多孔单层石墨烯为单元组装三维介孔碳骨架，研究其表面富集亲锂活性位点降低锂沉积过电位、其介孔的毛细作用增强熔融金属锂浸润、以及限域效应引导锂沉积这三类关系，并进一步提出稳定高效金属锂负极的构筑策略。

本项目立足于新一代高能锂电池急需稳定、高效碳基骨架金属锂负极的研究背景，针对碳晶格电子结构对其上锂成核与生长影响理论研究的空白和完美碳质实验载体电极的空缺，设计并实现以超平铜箔上生长的单层石墨烯单晶和多晶直接作为载体电极研究锂在其上电沉积成核与晶体生长规律，并进一步组装、阐明了三维碳骨架孔结构／界面性质与储锂特性构效关系，并设计实现高效、稳定三维碳基金属锂负极的构筑。在此基础上，将高效锂沉积电极推广到廉价且适合大规模应用的铜基材质，制备了多种三维复合金属锂复合电极。具体取得以下重要结果：首次设计了应用完美的单层石墨烯做研究的“试管”，阐明金属锂在碳晶格上电沉积的基本过程与机制，揭示了“石墨层表面的晶格缺陷与官能团能够促进金属锂电沉积高效成核”等一系列的科学发现，为研究碳晶格缺陷对金属锂电沉积影响规律、指导先进碳基金属锂负极的制备奠定实验方法基础；构筑了一种金属有机框架化合物（MOF）基介孔炭／氧化锌高效稳定金属锂负极，打开了MOF基材料在稳定金属锂沉积方面的研究思路；发明了一种用化学能驱动铜基合金表面原子移动的方法，首次实现了在1m2工业铜网上氧化锌亲锂层的制备，本思路能广泛的应用于多种铜基合金、简单高效，探索了先进金属锂负极集流体的工业应用的可能性。结合本项目工作，发表SCI收录论文11篇，申请发明专利两件，培养博士研究生、硕士研究生各3名。