Lithium-ion batteries (LIBs) are the most widely industrialized form of portable, rechargeable energy storage in over three decades. LIBs commonly use Super P carbon as a conductive additive. Super P is chemically similar to industrial waste produced via diesel combustion, and therefore shares chemical properties with diesel soot. Here we show how diesel soot particulate matter obtained postcombustion can be used as a conductive additive in LIBs.