Synergistic integration of conversion and alloying reactions in a hierarchical Sn-doped NiO-C-CNT framework for dendrite-free lithium metal batteries

Stabilizing lithium metal anodes requires the synergistic contributions of lithiophilic components, conductive frameworks, and nanostructuring. Nevertheless, strategies that integrate all three remain scarcely reported, and the fundamental understanding of lithiophilic materials, particularly their conversion-alloying reactions, remains unexplored. In this study, a three-dimensional hierarchical void host structure composed of Sn-doped NiO-carbon-CNT (HV-Sn-NiO-C-CNT) microspheres was synthesized via a one-pot spray pyrolysis process. Upon initial lithiation, Sn-doped NiO undergoes conversion and alloying reactions to form Li-Sn alloy, metallic Ni, and Li2O matrix. The lithiophilic Li-Sn alloy facilitates uniform lithium nucleation, metallic Ni provides conductive pathways, and the Li2O matrix contributes to mechanical buffering and interfacial stabilization, collectively enabling uniform lithium deposition. The hierarchical voids buffer the volume changes during lithium plating and stripping, while CNTs reduce local current density and suppress dendritic growth. DFT calculation revealed that Sn doping lowers lithium adsorption energy and enhances the electronic conductivity of NiO, providing a fundamental explanation for uniform, dendrite-free lithium deposition. Benefiting from these synergistic effects, HV-Sn-NiO-C-CNT anode delivers a Coulombic efficiency of 97% over 300 cycles in asymmetric cell. Symmetric cells with HV-Sn-NiO-C-CNT-Li electrodes exhibit lower voltage polarization and enhanced cycling stability for over 2000 h. Notably, full cells with the LiFePO4 (LFP) and LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode demonstrate robust cycling stability and high rate capability, indicating the practical applicability.