Reconstructing the Li+ solvation structure in quasi-solid polymer electrolyte for stable lithium metal batteries

Quasi-solid polymer electrolytes (QSPEs) have been attracted significant attentions due to their benefits for simultaneously improved safety and energy density of batteries. Developing electrolytes capable of forming a stable solid electrolyte interphase (SEI) layer is a great challenge for QSPE-based lithium (Li) metal batteries (LMBs). Herein, unlike previously reports that the reconstruction of Li + solvation structures in QSPE requires time-consuming bottom-up polymer synthesis, in current study, a facile approach has been developed to reconstruct the Li + solvation structures in QSPE by adjustment of the salt concentrations. The high proportion of Li + -anion complexes can effectively accelerate interfacial Li + diffusion, mitigate the decompositions of organic solvents and induces the formation of a LiF-rich SEI layer, contributing to suppressed Li-dendrite growth. As a result, the Li/QSPE-3/LiFePO 4 (LFP) cell performs an ultralong lifespan with capacity retention of 77.4% over 3000 cycles at 1 C. With a high-voltage LiCoO 2 cathode, the cell can stably cycle over 200 cycles at 25 °C (capacity retention of ∼83.8%). With accelerated ion transport dynamics due to the reconstructed Li + solvation structure, the QSPE-3 (the salt concentration is 3 M) is applicable in a wide temperature range. The Li/QSPE-3/LFP full cell exhibits 58.1% and 102.6% of discharge capacity at −15 and 90 °C, respectively, compared to those operated at 25 °C. This study demonstrates a facile yet effective approach on enhancing electrode/electrolyte interfacial stability, enabling the LMBs with simultaneously enhanced safety and high energy density.