Significantly improved capacity retention of lithium metal batteries enabled by a 1,3,5-Trioxane electrolyte additive

The practical application of lithium metal batteries is hindered by the heterogeneous solid-electrolyte interphase (SEI), which undergoes repeated cracking and reconstruction during cycling, thereby exacerbating lithium dendrite growth. To address this issue, we propose an in-situ reconstruction strategy for the SEI layer by introducing the functional additive 1,3,5-trioxane (TO), which helps to homogenize lithium transport and enhance mechanical stability. By participating in the Li + solvation structure, TO facilitates the formation of a homogeneous and mechanically robust SEI, which preferentially promotes the formation of a polyoxymethylene (POM) phase and enriches LiF content within the SEI. This tailored interface significantly improves the uniformity of lithium deposition and interfacial compatibility. In coin cells employing a high-loading LiNi 0.90 Co 0.05 Mn 0.05 O 2 cathode (7.37 mg cm − 2 ) and an ultrathin lithium anode (50 μm), the TO-modified electrolyte enables a capacity retention of 73.1% after 200 cycles at 0.5 C, substantially outperforming the conventional electrolyte that retained only 25.9%. These results demonstrate the promising potential of this electrolyte design for high-energy-density lithium metal batteries.