Design of 3D porous Cu scaffold structure with lithiophilic gradient for a highly stable lithium metal battery

Abstract

As demand for portable electronic devices and electric vehicles increases, there is growing interest in developing lithium-ion batteries (LIBs) with high energy density and high theoretical capacity. Among the anode materials, Lithium (Li) metal is considered as a promising anode material due to its high theoretical capacity (3860 mAh g-1) and lowest redox potential (-3.04 VSHE) compared to commercially used graphite anode. However, lithium metal anode (LMA) has problematic dendrite formation during charging/discharging, which causes severe problems such as increased polarization, volume expansion, and cell short circuit. One of the strategies to solve these issues is introducing 3D porous conductive scaffold (3D pCS). The 3D pCS possess high surface area, dispersing the local current density and thereby alleviating the growth of Li dendrites. Additionally, it offers enough space to accommodate the growth of Li. However, 3D pCS is electrically conductive, Li is preferentially deposited on top of the 3D pCS surface with short Li ion diffusion length. This increases the risk of cell short circuit and volume expansion. In this work, we propose 3D Ag@Cu pCS with lithiophilic gradient to enable inner deposition of Li to inhibit dendrite formation. For this purpose, we adopted a lithiophilic material on the bottom of the scaffold. In particular, a lithiophilic gradient was introduced into the scaffold to be more effective, by using hierarchical galvanic displacement from the 3D Cu pCS surface. 3D Ag@Cu pCS with lithiophilic gradient exhibits higher cycling capability (89.0% capacity retention after 110 cycles) and rate performance (99.6 mAh g-1 at 2C) compared to Cu foil and 3D Cu pCS. Furthermore, inner deposition of lithiophilic gradient 3D Ag@Cu pCS is confirmed by SEM images.