Accelerating lithium ion transport via increasing the entropy of the electrolyte for stable lithium metal batteries

Promoting inorganic-rich solid-electrolyte interphase (SEI) formation by constructing anion-rich solvated structures is a promising strategy for improving the long-term cycling of lithium-metal batteries. However, the increase of anions within the solvated structure inevitably reduces the coordination of Li+ with the solvent, which leads to a low lithium diffusion coefficient and a decreased lithium conductivity. Here, high entropy electrolyte is achieved by increasing the molecular diversity in electrolyte. Multiple anions (TFSI−, FSI−, NO3− and PF6−) presented in entropy electrolyte individually coordinate with Li+, creating a diverse and anion-rich solvation structure. The large variety of solvation structures leads to a diversified Li+ diffusion barriers in the electrolyte, which results in the increase of channels available for Li+ diffusion. Thus, three-dimensional diffusion with high Li+ diffusion coefficient occurs in HE electrolytes. Furthermore, the anion-rich solvation structures promote the formation of the inorganic-rich SEI. As a result, over 2000 h of reversible Li plating/stripping with a low overpotential less than 27 mV is achieved in Li||Li cell using electrolyte modified by high-entropy strategy. Besides, the Li||LFP full cell with a negative capacity/positive capacity (N/P) ratio of 4.52 exhibits remarkably enhanced cycling stability, retaining 83.6% of its initial capacity after 150 cycles. This strategy offers a novel approach for accelerating Li+ transport kinetics and constructing stable SEI in lithium metal batteries.