热压法构筑锂负极聚偏氟乙烯基双功能保护层的研究

锂金属具有高比容量(3860 mA·h/g)和低电化学电位(-3.04 V vs. SHE), 是一种极具潜力的新型电池负极材料. 然而, 锂金属电化学稳定性差, 导致电池循环寿命受限, 容易产生枝晶, 造成电池短路, 引发安全风险, 而其对空气及环境的高度敏感性也极大增加了电池制作的难度与成本, 限制了其应用推广. 改善锂金属负极的界面稳定性被认为是提升锂金属电池性能的重要途径. 本文通过简单直接的热压法在锂金属负极表面构筑了聚偏氟乙烯(PVDF)基双功能保护层, 使锂金属的空气稳定性提升至约120 min, 并延长了锂金属对称电池的循环寿命至约1200 h; 再通过在PVDF保护层内引入亲锂的SnO₂粒子, 形成的无机有机复合保护层可以通过原位合金化反应提供锂沉积的形核位点, 在保持良好循环稳定性的基础上进一步降低成锂沉积的过电位, 极化过电位从0.016 V降低到0.007 V. 含有该保护层的全电池展现出约200次的长循环寿命与90%以上的高容量保持率, 在3C高倍率下放电比容量仍达127 mA·h/g. 提出的双功能电极界面保护层策略能有效提升锂金属负极空气稳定性和电化学性能.

Hot-pressed PVDF-based Difunctional Protective Layer for Lithium Metal Anodes

Lithium metal has been considered a promising anode for next-generation batteries due to its high specific energy（3860 mA·h/g） and lowest redox potential（-3.04 V vs. SHE）. However， the poor electrochemical stability of lithium metal results in limited cycle life and short-circuit due to lithium dendritic growth. Poor environmental stability of lithium metal also increases production difficulty and cost. Improving the interface stability of lithium metal anode is considered as an important approach to optimize battery performance. Herein， a dual-functional polyvinylidene fluoride（PVDF） protective layer is fabricated on lithium anode surface using a simple hot-pressing method， effectively promoting air stability to 120 min and increasing cycle life of the symmetrical battery to 1200 h. In addition， by introducing SnO₂ nanoparticles， an inorganic-organic composite protective layer is constructed. The composite protective layer induces lithium nucleation sites by in?situ alloying， which greatly reduces lithium plating overpotential to 0.007 V and facilitates better cyclability of lithium metal anodes. The full-cell with this protective layer shows a long cycle life of 200 cycles with a capacity retention rate higher than 90% and a high discharge capacity of 127 mA·h/g at a current rate of 3C. The strategy proposed in this work for the dual-function interface protective layer can effectively improve the air stability and electrochemical performance of lithium metal anode.