Exploiting lithium-ether co-intercalation in graphite for high-power lithium-ion batteries

Abstract

The intercalation of lithium ions into graphite electrode is the key underlying mechanism of modern lithium&#8208

ion batteries. However, co&#8208

intercalation of lithium&#8208

ions and solvent into graphite is considered undesirable because it can trigger the exfoliation of graphene layers and destroy the graphite crystal, resulting in poor cycle life. Here, it is demonstrated that the [lithium&#8211

solvent]+ intercalation does not necessarily cause exfoliation of the graphite electrode and can be remarkably reversible with appropriate solvent selection. First&#8208

principles calculations suggest that the chemical compatibility of the graphite host and [lithium&#8211

solvent]+ complex ion strongly affects the reversibility of the co&#8208

intercalation, and comparative experiments confirm this phenomenon. Moreover, it is revealed that [lithium&#8211

ether]+ co&#8208

intercalation of natural graphite electrode enables much higher power capability than normal lithium intercalation, without the risk of lithium metal plating, with retention of &#8776

87% of the theoretical capacity at current density of 1 A g&#8722

1. This unusual high rate capability of the co&#8208

intercalation is attributed to the (i) absence of the desolvation step, (ii) negligible formation of the solid&#8211

electrolyte interphase on graphite surface, and (iii) fast charge&#8208

transfer kinetics. This work constitutes the first step toward the utilization of fast and reversible [lithium&#8211

solvent]+ complex ion intercalation chemistry in graphite for rechargeable battery technology.