  Lithium metal has been an attractive candidate as a next generation anode
material. Despite its popularity, stability issues of lithium in the liquid
electrolyte and the formation of lithium whiskers have kept it from practical
use. Three-dimensional (3D) current collectors have been proposed as an
effective method to mitigate whiskers growth. Although extensive research
efforts have been done, the effects of three key parameters of the 3D current
collectors, namely the surface area, the tortuosity factor, and the surface
chemistry, on the performance of lithium metal batteries remain elusive.
Herein, we quantitatively studied the role of these three parameters by
synthesizing four types of porous copper networks with different sizes of
well-structured micro-channels. X-ray microscale computed tomography (micro-CT)
allowed us to assess the surface area, the pore size and the tortuosity factor
of the porous copper materials. A metallic Zn coating was also applied to study
the influence of surface chemistry on the performance of the 3D current
collectors. The effects of these parameters on the performance were studied in
detail through Scanning Electron Microscopy (SEM) and Titration Gas
Chromatography (TGC). Stochastic simulations further allowed us to interpret
the role of the tortuosity factor in lithiation. By understanding these
effects, the optimal range of the key parameters is found for the porous copper
anodes and their performance is predicted. Using these parameters to inform the
design of porous copper anodes for Li deposition, Coulombic efficiencies (CE)
of up to 99.56% are achieved, thus paving the way for the design of effective
3D current collector systems.
