Dynamic Self-Organizing Lithium Bonds for High Energy Density Lithium Batteries

To enhance the electrochemical performance of silicon electrodes, it is essential to comprehensively understand their underlying lithium storage mechanisms. Unfortunately, the vast diversity of silicon anode types and compositions complicates efforts to accurately predict and validate these reaction processes. Accordingly, a structurally well-defined silicon-based model compound is in great need. Thus, we select methacrylate polyhedral oligomeric silsesquioxane (MAPOSS) as the subject for studying the lithium-silicon bonding mechanism due to its clear chemical structure and composition. Through detailed characterization of the morphological and chemical structural changes of MAPOSS before and after cycling, our results reveal an intriguing phenomenon: the synergistic interaction (here termed as "Dynamic Self-Organizing Lithium Bonds") between Si atoms in the core and carbonyl (C = O) groups in the side arms of MAPOSS promotes reversible dynamic Li⁺ ions storage. Density functional theory simulations further support this deduction. Furthermore, MAPOSS is employed as a binder in graphite anodes after polymerization. At 0.2 C, the resulting half-cell exhibits an impressive specific capacity exceeding 450 mAh g^-1 over 250 cycles. This study demonstrates that the integration of MAPOSS into the full cell configuration allows for a reduction in the N/P ratio and is expected to improve the overall energy density of the battery.