Pendant Length-Dependent Electrochemical Performances for Conjugated Organic Polymers as Solid-State Polymer Electrolytes in Lithium Metal Batteries

Construction of high elastic artificial SEI for air-stable and long-life lithium metal anode

Compared with other anode materials, Li metal anode has higher capacity density and lower electrode potential, which has been considered as one of the most promising anode materials. However, the unstable solid electrolyte interface (SEI) leads to Li dendrite growth and the infinite volumetric expansion of Li metal, which seriously hinders the stability and cycle life of Li metal batteries (LMBs). Here, a polyurethane elastomer (TPU) material with high elasticity and air stability is used as the artificial SEI of Li metal anode. Its designed synergistic effect of soft chain forging and hard chain segments not only gives TPU artificial SEI layer good electronic insulation, Li ion conductivity, Li dendrite growth inhibition, high elastic modulus and flexibility to adapt to Li volume expansion, but also has a significant air protection effect on the Li metal surface, so that the TPU coated Li foil will not occur obvious oxidation phenomenon after being placed in air for 45 min. The Li symmetric battery modified by TPU achieved a stable and long-term cycle performance of 1300 h at 1 mA/cm², it can also cycle stably at a high current density of 10 mA/cm². The Coulomb efficiency of the modified Li/Cu half-cell maintains at above 97% after 400 cycles. In addition, the full cell with LiFePO₄ cathode also delivers a very excellent long cycle stability with 90% capacity retention after 1500 cycles at 5 C. This surface modification strategy of SEI on lithium anode has has great research value and will help to improve the widely application of LMBs.