Abstract
Lithium metal batteries (LMBs), especially the "zero-excess" LMBs, or the so-called anode-free LMBs, are pivotal to the next-generation energy storage technologies. However, how to keep uniform Li deposition to effectively circumvent the formation of metallic Li dendrites is challenging. In fact, the formation of a stable inorganic-rich solid electrolyte interphase (SEI) has been found to improve the Li-ion flux which is critical for uniform Li deposition to ensure safety, longevity, and high efficiency of LMBs. Herein, copper foils with a (220) orientation exhibiting a high surface energy are designed to accelerate the formation of an inorganic-rich SEI layer for metallic Li plating and stripping in LMBs. However, this high surface energy decreases the surface mobility of lithium atoms, presenting obstacles to uniform nucleation and deposition. To address this challenge, a high-speed electroplating process in a methane-sulfonic acid-based bath is developed to produce the copper foils with highdensity grain boundaries. These boundaries serve as the preferential nucleation sites, improving the uniform distribution of lithium nucleus and resulting grains on the copper current collector surface. Furthermore, embedding a nanotwinned structure into these Cu foils decreases the atomic step density, reducing the number of random nucleation sites and enlarging the grain size of the uniform lithium deposit. The nanotwinned structure also promote the growth of an inorganic-rich SEI layer. The resulting (220)-oriented, fine-grained nanotwinned copper foil (Cu-NT(220)) serves as a high-performance current collector for LMBs. In full cells with an N/P ratio of 3.2, the Cu-NT(220) substrate retains 90.6 % of its initial capacity after 300 cycles, significantly outperforming the standard (220) orientation copper foil (Cu(220)) with capacity maintenance of only 53.8 %.