COF@NF锂电池宿主的制备及其抑制锂枝晶研究

Preparation of COF@NF as a Host Material and Its Inhibition of Lithium Dendrites

摘要:

目前，锂离子电池的发展受到能量密度限制，很难开发出能量密度超过300 Wh?kg^-1的锂离子电池，需寻找新的负极材料代替常规的石墨负极。金属锂因具有高的理论比容量（3 860 mAh?g^-1）、低的化学还原电位（-3.04 V vs.RHE）和密度（0.53 g?cm^-3）等优势，成为了下一代锂硫电池和锂空气电池的理想负极材料。但是，锂金属的无宿主性，使锂电池在充放电循环过程中面临着体积膨胀和难以控制的锂枝晶生长的挑战，极大地阻碍了锂金属负极的实际运用。因此，通过构建亲锂性界面以诱导锂金属均匀沉积，是解决上述问题的有效方法。同时，三维结构能够明显降低电池的绝对电流密度，这对于电池在大电流下的稳定循环是有帮助的。通过使用三嗪基有机框架材料（t-COFs）修饰泡沫镍表面作为亲锂界面，并将其作为锂金属负极的宿主来抑制锂枝晶的生长，在电流密度3.0 mA?cm^-2、沉积容量1.0 mAh?cm^-2的条件下，t-COF@NF-Li半电池能够稳定循环400圈，同时还保持着高的平均库伦效率和小的电压极化。另外，t-COF@NF-Li//Li对称电池，在电流密度1.0 mA?cm^-2、沉积容量1.0 mAh?cm^-2的条件下，能够稳定循环600 h，并且保持20 mV的低过电位。结果表明，t-COFs具有优异的电化学性能，说明在泡沫镍骨架上构建亲锂界面以抑制锂枝晶的形成是可行的，该方法对于构建高性能锂金属电池有推进意义。

Abstract:

At present， the development of lithium-ion batteries is limited by energy density， which lead to the difficulty of developing more than 300 Wh?kg^-1 lithium-ion batteries. Thus， researchers have to find new anode materials to replace the conventional graphite anode. Lithium metal has the advantages of a theoretical specific capacity of up to 3 860 mAh?g^-1， the lowest chemical reduction potential （-3.04 V vs standard hydrogen electrode）， and low density （0.53 g?cm^-3）， which makes it an ideal anode material for the next generation of lithium-sulfur and lithium-air batteries. However， due to the "host-free" nature of lithium metal， batteries often face challenges such as volume expansion and difficult to control lithium dendrite growth during the charge-discharge cycle， which greatly hinders the practical use of lithium metal anode. Studies have shown that constructing a lithium-philic interface to induce uniform deposition of lithium metal is an effective method to solve the above problems. At the same time， the three-dimensional structure can significantly reduce the absolute current density of the battery， which is helpful for the stable cycle of the battery at high current. In this paper， the surface of nickel foam was modified by using triazine-based organic framework materials （ t-COFs ） as a lithium-philic interface， and the modified nickel foam was used as the host of lithium metal anode to inhibit the growth of dendrites. The results show that the t-COF@NF-Li half cell can cycle stably for 400 cycles while maintaining a high average coulomb efficiency and low voltage polarization under a current density of 3.0 mA?cm^-2 and a deposition capacity of 1.0 mAh?cm^-2. Additionally， the t-COF@NF-Li//Li symmetric cell can cycle stably for 600 h and maintain a small overpotential of 20 mV under a current density of 1.0 mA?cm^-2 and a deposition capacity of 1.0 mAh?cm^-2. The excellent electrochemical properties indicate that it is feasible to construct a lithium-philic interface on the foam nickel skeleton for inhibiting the formation of lithium dendrites， and this method holds great significance for constructing high-performance lithium metal batteries.