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Construction of a High-Stability and Low-Nucleation-Barrier Cu3Sn Alloy Layer on Carbon Paper for Dendrite-Free Li Metal Deposition.

The construction of three-dimensional lithiophilic hosts is one of the most effective approaches for achieving the uniform nucleation and alleviating the volume changes of the Li metal. Unfortunately, some lithiophilic materials suffer from severe mechanical degradation resulting from the large volume expansion during lithiation, which causes a heterogeneous Li deposition. Herein, a low-nucleation-barrier Cu3Sn alloy layer on a carbon paper (Cu3Sn/CP) is constructed by a facile co-electrodeposition method for the Li anode framework. Density functional theory calculations show that the Cu3Sn alloy has a higher binding energy (-2.31 eV) than pure Sn (-1.97 eV) due to the electron-deficient state of Sn in the alloy phase, which enables the lithiophilic Sn to have increased affinity for Li. Additionally, the uniformly distributed Cu particles can evenly disperse the electric field on the surface of the carbon fiber and act as a "metal barrier" to inhibit the volume expansion of the Sn particles during lithiation, thereby enhancing the electrochemical stability of the alloy modification layer. As a result, the Cu3Sn/CP anode framework exhibits an exceptionally low nucleation overpotential (∼10 mV), a high and steady Coulombic efficiency (>98.5% for more than 200 cycles), and a long lifespan up to 1150 h. The full cells with LiFePO4 as a cathode show favorable cycling performance at 1 C with a capacity retention rate of 95.2%. The construction of the Cu3Sn alloy layer in this work sheds light on the design of a high-stability lithiophilic host for the dendrite-free Li metal anode.