Unraveling the Evolution of Lithium Plating and Stripping in Anode-Free Lithium Metal Batteries Via Operando Neutron Depth Profiling.

Anode-free lithium metal batteries (AFLMBs) represent a promising pathway toward high-energy-density storage systems. However, their cycling lifetime is fundamentally constrained by uncontrolled spatial distribution of lithium and loss of active lithium during plating and stripping. This study employed a vacuum-compatible operando neutron depth profiling (NDP) cell based on a liquid-electrolyte anode-free Cu||Li1.2Ni0.13Co0.13Mn0.54O2 full cell to quantitatively track the depth-resolved evolution of Li plating and stripping under varied charging rates (0.2, 0.5, 1, and 2 C). Results demonstrate that charging rate critically governs lithium nucleation sites and spatial distribution: at 0.2 C, sparse nucleation sites promote lithium growth toward the electrolyte; high rates (1 and 2 C) yield loose mossy deposits, where upper layers readily lose electrical contact during stripping, forming "dead lithium." In contrast, 0.5 C provides a favorable balance between electrical connectivity during stripping and deposit structural stability, leading to relatively optimal cycling performance among the investigated rates. This work systematically elucidates how charging rate modulates lithium plating and stripping dynamics, providing direct, quantitative experimental evidence to guide rational design of cycling protocols for AFLMBs.