Lead-Carbon Composites for Sodium-Ion Batteries

Lead (Pb) is of interest as a sodium alloying compound to increase the volumetric energy density of sodium-ion batteries. However, Pb has not been shown to cycle reversibly with the carbonate-based electrolytes common in sodium- and lithium-ion batteries. Moreover, the 387% volume expansion of Pb when fully sodiated results in continual sodium inventory loss at the negative electrode, even when far stabler glyme-based electrolytes are used. A lead-carbon (Pb-C) composite material, analogous to silicon-carbon composites, may be able to overcome these electrolyte stability issues. In this work, several Pb-C composites are shown to incorporate up to 27% Pb by mass and are synthesized by mechanical mixing of Pb and cellulose acetates followed by pyrolysis and carbon coating using chemical vapour deposition. The best Pb-C sample can be cycled more than 100 times in carbonate electrolyte with only 14% lower specific capacity than with monoglyme electrolyte. This is far superior to pure Pb and Pb blended with hard carbon, but additional work is encouraged to improve their performance further.