Shin Woochul, Manthiram Arumugam
Texas Materials Institute, University of Texas at Austin, Austin, Texas 78712, United States.
ACS Appl Mater Interfaces. 2022 Apr 20;14(15):17454-17460. doi: 10.1021/acsami.2c01980. Epub 2022 Apr 6.
Lithium-metal batteries with zero excess lithium on the anode side paired with a fully lithiated cathode are regarded as a form of the highest energy-density configuration. Unfortunately, the continuous lithium loss over cycling from a limited amount of the lithium reservoir significantly degrades the overall cell performance in the anode-free system. To mitigate the deterioration, modifying the current collector for enhanced lithium cycling is an indispensable route. Here, we apply a Ag/Cu ion exchange to precipitate micro-sized Ag particles on the Cu current collector to enhance the lithium reversibility via a (de)alloying process. We show a smoother morphology of lithium upon alloying, which leads to a lowered nucleation potential as well as increased average Coulombic efficiency in Li||Cu cells regardless of electrolyte formulation. The preferred lithium adsorption on Ag and AgLi over Cu is demonstrated using density functional theory calculations, which supports that Li forms a gamma-phase alloy in the last stage rather than being deposited beneath the alloy. Lastly, this simple Cu foil modification enhances lithium reversibility and reduces its nucleation barrier, thus mitigating the capacity fade of Cu||LiFePO with reduced polarization.
阳极侧无过量锂且与完全锂化阴极配对的锂金属电池被视为最高能量密度配置的一种形式。不幸的是，在无阳极系统中，由于锂储存量有限，循环过程中锂的持续损失会显著降低电池的整体性能。为了减轻这种恶化，改进集流体以增强锂循环是必不可少的途径。在此，我们应用银/铜离子交换在铜集流体上沉淀出微米级银颗粒，通过（脱）合金化过程提高锂的可逆性。我们展示了合金化时锂更平滑的形态，这导致锂铜电池中的成核电位降低以及平均库仑效率提高，而与电解质配方无关。使用密度泛函理论计算证明了锂在银和银锂上比在铜上更倾向于吸附，这支持锂在最后阶段形成γ相合金而不是沉积在合金下方。最后，这种简单的铜箔改性提高了锂的可逆性并降低了其成核势垒，从而减轻了磷酸铁锂||铜电池的容量衰减并降低了极化。
