Porous copper foam co-operation with thiourea for dendrite-free lithium metal anode

Abstract

With the rapid development of electric vehicles and portable electronic devices, traditional lithium-ion batteries with graphite anodes cannot satisfy demands for increased energy density. Lithium metal, with a high theoretical specific capacity (3860 mAh·g−1), low density (0.534 g·cm−3), and the lowest potential (−3.040 V vs. standard hydrogen electrode), has received much attention as an ideal anode material for next-generation energy storage devices. However, the uncontrolled growth of lithium dendrites and low Coulombic efficiency caused by negative side reactions have severely hindered the development of lithium metal batteries. Here, we propose a strategy based on the synergistic effect between a porous copper foam and thiourea, which uses the “super-filling” effect of thiourea molecules to achieve the uniform deposition of lithium metal on the surface of the porous copper foam. The unique curvature enhance coverage mechanism of thiourea molecules can accelerate Li deposition rate in grooves and achieve “super-filling” growth. The porous copper foam was obtained through simple multi-step processing. Scanning electron microscopy images showed many small pores evenly distributed on the surface; these pores acted as nucleation sites for lithium deposition. With the effect of thiourea, lithium was preferentially deposited in the small pores and then filled to the top, and finally deposited uniformly on the surface of the porous copper foam. The morphologies of the different electrodes deposited with capacities of 1, 3, and 10 mAh·cm−2 demonstrated the synergistic effect between the porous copper foam and thiourea, which can inhibit the growth of lithium dendrites. Through this strategy, stable lithium plating/stripping over 500 h was achieved at a current density of 1 mA·cm−2 with a fixed capacity of 1 mAh·cm−2 while maintaining a voltage hysteresis below 20 mV. Meanwhile, greatly enhanced Coulombic efficiency and longer cycle life times were achieved: the Li||LiFePO4 full cell maintained 94% capacity after 300 cycles at 5C. Exploiting the synergy between the electrolyte and framework provides a novel approach for fabricating advanced lithium metal batteries. This work thus details a novel strategy for lithium anode protection that may also be extended to other metal anodes, thereby facilitating the development of next-generation energy storage devices.