Yang Junfeng, Wang Xusheng, Huang Shizhi, Zhang Xinxiang, Chen Jitao
Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.
Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
ACS Appl Mater Interfaces. 2020 May 6;12(18):20423-20428. doi: 10.1021/acsami.0c01957. Epub 2020 Apr 22.
The room-temperature liquid anode is a feasible method for building dendrite-free alkali-metal-based batteries. The Na-K phase diagram shows a eutectic point as low as 260.53 K with a long liquid range below 298 K with the molar fraction of potassium ranging from 30.48 to 84.99%. However, the NaK alloy exhibits a very high surface tension preventing it from wetting the current collector surface. Herein, a novel homogeneous dual solid-liquid composite in which the liquid alloy is fixed by the solid NaSn phase and perfectly stuffed into the grid of the mesh has been designed and fabricated. Based on the liquid range of the NaK alloy, the Na-K-Sn mixture possesses a theoretical specific capacity of 768 mAh g. The symmetric cells of the Na-K-Sn@mesh electrodes cycled at 2.0 mA cm with 1.0 mAh cm showed little fluctuations with the stable overpotential of ∼200 mV for 550 h, and the full cell coupled with NaV(PO) showed an initial discharge capacity of 103 mAh g at 2 C with a retention of 90% after 800 cycles. When the high-loading NaV(PO) electrode is applied in the full cell, a stable cycling life is still maintained with a good capacity retention of 86% over 190 cycles (2.7 mAh cm) and 91% over 60 cycles (5.2 mAh cm).
室温液态阳极是构建无枝晶碱金属基电池的一种可行方法。Na-K相图显示其共晶点低至260.53 K，在298 K以下有很长的液相范围，钾的摩尔分数为30.48%至84.99%。然而，NaK合金表现出非常高的表面张力，使其无法润湿集流体表面。在此，设计并制造了一种新型的均匀双固液复合材料，其中液态合金由固态NaSn相固定并完美填充到网格中。基于NaK合金的液相范围，Na-K-Sn混合物的理论比容量为768 mAh g。Na-K-Sn@网格电极的对称电池在2.0 mA cm²、1.0 mAh cm²的条件下循环，在550 h内过电位稳定在约200 mV，波动很小，与NaV(PO₄)₂耦合的全电池在2 C下的初始放电容量为103 mAh g，800次循环后保持率为90%。当高负载NaV(PO₄)₂电极应用于全电池时，在190次循环（2.7 mAh cm²）中仍保持稳定的循环寿命，容量保持率良好，为86%，在60次循环（5.2 mAh cm²）中为91%。
