Combined X-ray computed tomography (X-CT) and electrochemical analysis of electrolyte-regulated stability of Li-metal anodes

Rechargeable Li metal batteries are regarded as a pragmatic solution in the pursuit of cell-level energy densities exceeding 500 Wh kg -1 . However, their stable operation remains a formidable challenge, primarily due to the dendritic and heterogeneous Li plating/stripping behavior of the Li metal anode, which is strongly influenced by electrolyte chemistry. Herein, we employ synergetic X-ray computed tomography (X-CT) and electrochemical characterization to examine electrolyte-dependent stabilization of Li metal interfaces and structural integrity. X-CT analysis uncovered Li plating/stripping dynamics and crack propagation in ester-based (ES) and ether-based (ET) electrolytes We reveal that, compared to conventional ES electrolytes, advanced ET electrolytes markedly enhance the homogeneity and densification of Li deposition, effectively suppressing dendrite formation and mitigating electrode structural degradation. This improvement is attributed to the enhanced stability of electrode structure, coupled with accelerated Li + transport kinetics. With a 50 μm-thick electrode, Li||Li symmetric cells exhibit remarkable longevity, sustaining stable operation for over 1200 hours at 1 mA cm -2 and 1 mAh cm -2 , and extending to 2000 hours at 1 mA cm -2 and 2 mAh cm -2 . When applied to practical full cells with a high cathode loading of 4 mAh cm -2 and a 50 μm-thick bare Li electrode, LiNi 0.95 Mn 0.03 Co 0.02 O 2 (NMC9532) ||Li cells demonstrate superior capacity retention, 96% after 100 cycles and 74% after 200 cycles at 0.3 C, outperforming their counterparts with carbonate-based electrolytes (50% retention after 200 cycles under identical conditions). This work offers valuable insights into electrolyte-dependent Li plating behavior and the evolution of the electrolyte/electrode interface under practical conditions, paving the way for the development of high-energy-density Li metal batteries.