Synergistic effect of infinite and finite solid solution enabling ultrathin Li–Cu–Ag alloy toward advanced Li metal anode

Abstract

Ultrathin Li-rich Li–Cu binary alloy has become a competitive anode material for Li metal batteries of high energy density. However, due to the poor-lithiophilicity of the single skeleton structure of Li–Cu alloy, it has limitations in inducing Li nucleation and improving electrochemical performance. Hence, we introduced Ag species to Li–Cu alloy to form a 30 μm thick Li-rich Li–Cu–Ag ternary alloy (LCA) anode, with Li–Ag infinite solid solution as the active phase, and Cu-based finite solid solutions as three-dimensional (3D) skeleton. Such nano-wire networks with LiCu₄ and Cu_xAg_y finite solid solution phases were prepared through a facile melt coating technique, where Ag element can act as lithiophilic specie to enhance the lithiophilicity of built-in skeleton, and regulate the deposition behavior of Li effectively. Notably, the formation of Cu_xAg_y solid solution can strengthen the structural stability of the skeleton, ensuring the geometrical integrity of Li anode, even at the fully delithiated state. Meanwhile, the Li–Ag infinite solid solution phase can promote the Li plating/stripping reversibility of the LCA anode with an improved coulombic efficiency (CE). The synergistic effect between infinite and finite solid solutions could render an enhanced electrochemical performance of Li metal batteries. The LCA|LCA symmetric cells showed a long lifespan of over 600 h with stable polarization voltage of 40 mV, in 1 mA·cm⁻²/1 mAh·cm⁻². In addition, the full cells matching our ultrathin LCA anode with 17.2 mg·cm⁻² mass loading of LiFePO₄ cathode, can continuously operate beyond 110 cycles at 0.5C, with a high capacity retention of 91.5%.Kindly check and confirm the edit made in the article title.OK

Graphical abstract