Non-clusters pseudo-bilayer solvation sheaths for driving low temperature high power lithium ion batteries

Abstract

High concentration electrolytes attract significant attention in low temperature electrolyte systems due to their ability to effectively reduce the desolvation energy barrier of lithium ions. However, the actual low temperature electrochemical performance of LIBs using these high concentration electrolytes remains unsatisfactory. Researchers usually attribute this poor performance to increased viscosity, reduced wettability, and a sharp decline in conductivity at low temperatures. However, these traditional views alone are not enough to reveal the underlying nature of the poor electrochemical performance. Herein, we explore the microscopic mechanisms underlying the poor electrochemical behavior of high concentration electrolytes under low temperature conditions at the molecular level. Using in situ low temperature Raman spectroscopy, we reveal for the first time that the formation of large solvated ion clusters is the fundamental reason for the unsatisfactory electrochemical behavior of high concentration electrolytes at low temperatures. To address this, we propose the “pseudo-bilayer solvation sheath” strategy to suppress the formation of large ionized clusters, thereby enhancing lithium ion transport at low temperatures, especially during the desolvation process from the electrolyte to the electrode surface. As a result, the optimized electrolyte enables an NCM811//graphite full cell to achieve rapid charging within 30 min at -20 °C, with a high capacity retention rate of 55.4%.