可规模化的原位电化学金属锂负极制备及其应用研究

Lithium metal anode has the advantage of high theoretical capacity (3860 mA h g-1), low density (0.59 g cm-3) and low potential (-3.04 V vs. SHE). It has been considered as the best anode for next generation of high energy storage batteries. However, there are two main difficulties hindering the wide application of lithium metal anodes, as the lithium dendrites growth because of uneven lithium deposition and the reconstruction of electrode-electrolyte interface during the cycling thus reduce the coulombic efficiency and cycle life. To address above problems, here we propose the scalable electrochemical production of lithium metal anode, in which combining the multi-scale component framework with the self-repairing artificial SEI layer. The larger scale 3D skeleton of the framework acts as a conductive collector, which inhibits the dramatic volume change of lithium metal during discharge and charge while the lower dimensional nanostructure regulates the distribution of the surface electric field and alleviates the formation of lithium dendrite. The in-situ electrodeposition of lithium metal anode also constructs a stable electrolyte-electrode interface (SEI) layer simultaneously. The leveling agent slows down the deposition rate on the lithium protrusion to alleviate the growth of lithium dendrite and level the surface of lithium anode. The preparation of the composite lithium metal anode and its application in high energy density lithium-sulfur batteries provide the scientific basis and reference for the practical application of lithium metal anode.

锂金属负极具有高理论比容量（3860 mA h g-1）、低密度（0.59 g cm-3）和低电极电势（-3.04V vs. SHE）的优势，被认为是下一代电池的理想负极材料。目前的锂金属负极主要存在两个方面的点：不均匀的锂沉积产生树枝状的锂枝晶；锂金属负极在循环过程中电极/电解液界面的不断重构使得库伦效率降低及循环寿命不足。为解决以上难题，本项目提出将多组分跨尺度的框架材料与可自修复的人工SEI膜相结合，原位电化学沉积制备金属锂负极。其中，较大尺度的三维骨架充当导电集流体，抑制锂金属剧烈的体积变化；较小尺度的三维骨架调控表面电场的均匀分布，缓解枝晶问题；可控的原位电沉积工艺，构造稳定电解液/电极界面；运用整平剂减缓突出点上沉积的速率，达到抑制突出生长和整平的目的。通过复合锂金属负极的制备和高能量密度锂硫电池研究，为锂金属负极的实际应用提供基础与借鉴。

在过去的数十年里，锂离子电池发挥着重要的作用。然而，随着社会和科技的发展，锂离子电池的理论容量限制使其难以满足更高能量密度的需求。因此，具有极高理论容量（3860 mAh g-1）和最低电极电势（-3.04 V vs. SHE）的锂金属负极被视为下一代理想负极材料而被复兴研究。锂金属负极目前仍被两大问题所困扰：1.锂枝晶生长；2.不稳定的电极/电解质界面。为了解决以上问题，将锂金属负极推向实用化，本项目将多组分跨尺度的框架材料（功能化碳骨架、镍骨架）和稳定的人工SEI膜（植酸衍生混合有机无机SEI层、银盐处理得到的混合离子/电子导体中间相层）联用，再结合对电解液的改性（硫脲、聚乙二醇200整平剂，硅基弱溶剂化电解液，新型支化固态电解质），实现了无枝晶的金属锂沉积和稳定的锂金属电池充放电。具体而言，项目研究所获得的复合三维金属锂负极整体比容量超过1000 mAh g-1，并可重复批量制备，满足实际高能量密度电池的应用需求。项目所开发的用于锂金属电池的硫脲整平剂，能够使组装的磷酸铁锂电池在5.0 C的大倍率循环650圈以后仍保持90%的容量。项目的研究成果，能够满足高效原位电化学沉积制备复合金属锂负极的要求，为锂金属负极的实际应用提供基础与借鉴。