亲锂聚合物与超薄纳米金属层协同 抑制锂枝晶生长

使用锂金属作为负极的金属锂电池能量密度高，但存在锂枝晶引起的循环寿命差和安全性能低等关键问题。在电化学沉积过程中，锂离子在集流体表面的不均匀分布是锂枝晶生长主要原因。因此，调控电极表面锂离子浓度和电场的均匀分布是抑制锂枝晶的根本策略。本论文通过在金属锂负极表面修饰纳米金属层以及亲锂聚合物，协同作用均匀电场和离子分布从而保证锂金属均匀沉积，缓解枝晶生长。

通过在CuCl2/DMSO溶液中的置换反应，在锂金属表面构筑一层均匀的3D纳米铜层并修饰一层锂离子传导率高的Li-Nafion膜，通过调控锂离子均匀沉积行为协同抑制锂金属负极的副反应，有效抑制了锂枝晶的生长。在金属锂表面原位生长的3D纳米铜层能够在电极表面提供均匀的电场，可以调控锂离子沉积行为；同时Li-Nafion膜具有均匀化锂离子通量，并为电极提供持续保护的作用。经过这两个修饰层的协同作用，NCuLi||LiCoO2全电池在经过500圈循环后，其容量仍然有122 mAh g-1，容量保持率为90.4%。

在AgTFSI/DME溶液中利用原位表面取代法在金属锂负极表面修饰一层亲锂纳米银层，同时采用柔韧性更好的壳聚糖磺酸锂作为保护层，利用两者的协同作用成功制备出稳定的锂金属负极。其中亲锂纳米银具有降低锂沉积过电位的功能，可以引导锂均匀沉积，同时壳聚糖磺酸锂具有保护锂金属负极的作用。在亲锂纳米银层与壳聚糖磺酸锂协同作用下，CAgLi||LiCoO2全电池在循环350圈后，其容量仍然有119 mAh g-1，容量保持率为83.8%。

本论文从调控锂离子沉积行为的角度出发，同时均匀化锂离子通量和界面的电场分布，成功制备了高稳定性的锂金属负极，为解决锂金属枝晶问题提供了新思路。

Lithium metal batteries with ultra-high theoretical energy density suffer from key issues such as poor cyclic stability and serious safety issues. However, the fundamental reason for the growth of Li dendrites is the uneven deposition of Li ions on the electrode surface. Therefore, regulating uniform conduction of Li ions and constructing evenly distributed electric fields at the electrode interface is critical to realizing dendrite-free Li metal anodes. In this article, the method of modifying the nano-metal layer and lithiophilic polymer on the surface of the Li metal anode was proposed. The synergistic effect between regulating uniform Li-ions deposition behavior by the nano-metal layer and homogenizing Li-ions flux through the lithiophilic polymer effectively inhibits the growth of Li dendrites.

In this experiment, a uniform 3D nano-copper layer and Li-Nafion film with good ion conductivity were constructed on Li metal anode. The 3D nano-copper layer grown on the surface of Li metal anode through an in-situ way could provide a uniform electric field near the electrode surface, which could regulate the deposition behavior of Li ions. Meanwhile, with high Li-ions conductivity and good flexibility, the Li-Nafion film could ameliorate Li-ions conduction and provide continuous protection for Li metal anode. After the modification, the NCuLi symmetric cell showed better cycling stability after 800 h, and the NCuLi||LiCoO2 full cell exhibited stable cycling performance, with a capacity retention rate of 90.4% after cycling for 500 cycles.

In addition, a layer of lithiophilic nano-silver layer was constructed on the surface of Li metal anode by in-situ surface substitution method, and a more flexible ionic polymer lithium chitosan sulfonate was used as the interface protection layer. Lithophilic nano-silver has the functions of reducing the overpotential of Li deposition and improving the efficiency of interfacial charge transfer, which could guide the uniform Li deposition behavior. Simultaneously, lithium chitosan sulfonate could fast and uniformly promote the conduction of Li ions and protect Li metal anode. Due to this synergistic effect, the specific discharge capacity of CAgLi||LiCoO2 full cell had been improved significantly after cycling for more than 350 cycles, with a capacity retention of 83.8%.

In this paper, from the perspective of regulating Li-ions deposition behavior, by simultaneously homogenizing the Li-ions flux and the electric field distribution at the interface, we have successfully prepared highly stable Li metal anodes, which provides a novel idea for the theoretical study of suppressing Li dendrite growth.

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