深度充放电贫锂复合负极的力学性质及界面调控研究

Lithium metal is with high specific capacity and low reduction potential, which has become one of the most promising anode materials for next-generation of high-energy-density batteries. The realizing of high-energy-density devices highly relies on the fully and effectively utilization of active species, whereas the usage of largely excess lithium limits the practical application of lithium metal battery (LMB). The lithium anode with limited Li excess experiences huge volume change and larger proportion of loss under deep-cycling conditions, which make it much easier to fail. In this project, we propose a templating approach towards tunable lithium-hosting spaces. Three-dimensional ordered macro-porous carbon-based frameworks are derived from metal organic frameworks (MOF) to obtain the lithium composite electrode. Combining the regulation of pre-reserved lithium-hosting space and adjusting the mechanical property of the carbon-based framework, we will design LMB adaptable to volume changes under deep-cycling conditions. The composition and interface properties of the framework will be adjusted through careful engineering of a variety of MOF precursors. The nucleation and growth of lithium metal under the confinement of carbon-based framework will be studied, through which the Coulombic efficiency of the lithium deposition/dissolution reaction is expected to be enhanced and efficient lithium composite anode will be developed under deep-cycling conditions. This project will provide important insights into the mechanism and practical application of lithium metal battery with limited lithium excess.

锂金属由于其比容量高、工作电势低，是下一代高能量密度电池最有潜力的负极材料之一。高能量密度的实现依赖于电池活性物质的充分、高效利用，而过量锂的使用制约了锂金属电池进一步走向实用化。贫量锂在深度充放电下体积变化巨大、锂损失严重，使其更易失效。本项目利用模板法定制载锂空间，以金属有机框架衍生材料构筑三维有序大孔碳基框架，制备锂复合负极；通过精确平衡锂的预留空间及碳基框架的力学性质，获得在深度充放电下可适应电极体积变化的锂金属电池；利用金属有机框架的多样性调控三维碳框架的成分和界面性质，研究锂在限域作用下的形核、生长行为，提升锂沉积/溶解反应的库伦效率，获得深度充放电下高效稳定的锂复合负极。项目的实施为探索和完善贫锂复合负极在深度充放电下的反应机制具有重要的理论价值，同时对推动高能量密度锂金属电池的研发和实用化具有重要意义。

锂金属电池的能量密度高，是极具发展应用前景的下一代高比能电池。然而，由于锂金属负极在循环过程中面临体积变化大、副反应多、易产生枝晶等问题，限制了锂金属电池的实际应用，尤其是在为了满足高能量密度的要求、需要负极只包含有限过量锂的条件下。本项目引入锂金属的三维支撑框架，通过三维框架的界面修饰，结合电解液的调控，构建高效稳定的锂金属负极；提升在低N/P比，即锂负极深度充放电条件下锂金属电池的性能。具体开展了以下方面的工作：. 1. 制备了一种LiNO3修饰的电导梯度骨架，LiNO3可引导生成富氮的SEI，骨架的梯度导电结构可促进锂离子“自下而上”进行定向沉积，使锂复合负极具有更高的空间利用率和循环寿命。在N/P比为2.3的条件下，和NCM811高压正极匹配而成的全电池可进行稳定循环。进一步装配的准固态高压锂金属电池可在1C条件下释放191.4 mAh g-1的初始容量，循环100圈后仍有78.2%的容量保持率。. 2. 通过锂离子与冠醚形成超分子结构，可在锂负极表面形成静电屏蔽层以调节锂金属沉积并抑制枝晶的形成；同时，可改变双电层的成分，生成以有机物为主导的SEI，提高了SEI的柔韧性，减少了死锂的产生。锂负极过量200%的全电池在100次循环后的容量保持率仍为100%。. 基于本项目的研究成果，在Energy Storage Materials、Advanced Materials等期刊发表论文6篇，得到研究者的广泛引用与评价。项目为提高深度充放电下锂负极的性能提供了有价值的科学探索和技术支撑。