AN ADVANCED TOOL FOR THE SELECTION OF ELECTROLYTE COMPONENTS FOR RECHARGEABLE LITHIUM BATTERIES

摘要

The solid electrolyte interphase (SEI) plays a key role in lithium-metal, lithium-alloy and lithium-ion batteries. The SEI has at least two-layered structure. The first layer close to the lithium side consists of fully reduced (thermodynamically stable) anions such as F~-, O~(2-), S~(2-) and other elements such as As, B, C (or their lithiated compounds). A second layer is composed of Li_2CO_3 and/or organic materials. The SEI composition and properties depend strongly on electrolyte composition. Rapid formation of the SEI is important in all lithium batteries, especially in the case of lithium-ion cells with graphite anodes. Hence SEI precursors must have high i_0 for reduction. As it is difficult to measure io on solid electrodes it is suggested to use the data bank for the rate constant for the reduction of electrolyte components by solvated electrons (e'_(aq)~-). We have demonstrated that the rate constants of the reactions of solvated electrons with electrolyte components and impurities correlate well with the stability of these substances towards lithium. The rate constants (k_e) for these reactions are suggested to be used as a tool for the selection of electrolyte components. Good correlation was found between k_e and SEI formation voltage and composition.