The study of electrochemical properties and lithium deposition of graphite at low temperature

The electrochemical properties of graphite with various degrees of graphitization, contents of rhombohedral phase, and surface areas were electrochemically investigated at 25 °C and −5 °C. The degree of graphitization and the amount of rhombohedral phase affected the samples’ lithium intercalation/deintercalation and surface deposition. The reductions of electrolyte conductivity and lithium ion diffusion in the graphite interlayer at −5 °C lowered the graphite's capacity. Lithium deposition also occurred on the graphite's surface. Highly graphitized samples were affected greatly by temperature, showing large capacity loss at low temperature. Increased rhombohedral phase facilitated lithium deposition on the graphite's surface as lithium ions did not insert into the graphite interlayers and accumulated at its edged planes. Increasing the pathways for lithium ion intercalation could facilitate lithium intercalation and reduce lithium deposition.

► The graphite samples are electrochemically investigated at 25 °C and −5 °C. ► The graphite with high graphitization shows a big reduced capacity by decreasing temperature. ► The graphite with higher rhombohedral phase in graphite can easily form a lithium deposition on the graphite surface.