Promoting Lithium Electrodeposition Towards the Bottom of 3-D Copper Meshes in Lithium-Based Batteries

Abstract

Lithium (Li) has been considered as the promising negative electrode in rechargeable batteries, owing to the negative redox potential (-3.04 V vs. SHE), low density (0.534 g/cm3), and high theoretical specific capacity (3,860 mAh/g). However, the non-uniform stripping/plating process of the metallic Li is still challenging.[1] As one of the solutions, three-dimensional (3-D) metallic scaffolds were introduced to the negative electrode. The uniform electric field applied in the porous scaffolds could suppress the dendritic growth of the Li during the plating process. In addition, a decrease in the effective current density prolonged Sand’s time.[2] However, such a Li deposition mainly proceeded on the top surface and led to rapid surface clogging due to the strong surface electric field. In this presentation, we show the preferred Li deposition inside the 3-D copper (Cu) scaffold using gold nanoparticles (Au NPs). The lower Li nucleation energy barrier on the Au surface than that on the typical Cu current collector was investigated intensively.[3] However, the role of Au for spatially promoting Li deposition was not studied in depth. We added the Au NPs with an average particle size of ~7.5 nm to the bottom of 3-D Cu. The Au NPs with a total ~28 nmol reduced the charge-transfer resistance, which suggested the fast Li nucleation on the Au. In addition, we coated aluminum oxide (Al2O3) layer with ~ 26 nm of thickness on the top surface of 3-D Cu scaffold through the atomic layer deposition (ALD) process. This insulating layer further suppressed the Li deposition on the surface. As a result, apparent Li deposition towards the bottom of 3-D Cu was clearly demonstrated. During Li plating/stripping cycles, the surface clogging of the 3-D Cu/Au by an accumulation of solid electrolyte interphase (SEI) was also dramatically alleviated even in the absence of Al2O3 layer. It demonstrated the continuous Li deposition towards the bottom of the 3-D Cu/Au scaffold. Besides, symmetric 3-D Cu/Au cells exhibited over 95 % of Coulombic efficiency (CE) for ~120 cycles. The full cells comprised of the 3-D Cu/Au and LiFePO4 (LFP) electrodes delivered stable 300 cycles with a capacity of ~140 mAh/g at 1 C-rate. I will discuss the detailed role of the Au NPs and the Al2O3 layer, and comparative cell performances in the presentation.