Incorporating graphite from pencils as a component of lithium-ion batteries

Rechargeable lithium-ion batteries operate on reversible insertion of lithium ions into host anode and cathode active materials to realize energy storage, and graphite-based anode is one of the many components of a lithium-ion battery where oxidation, or transfer of electrons occurs. With global energy consumption rising by 5% in 2021 alone, and the United States throwing away 1.6 billion pencils annually, sustainable power options are essential for the future. Here we hypothesized that graphite derived from pencils could be directly used for lithium-ion battery anode applications, especially from pencil stubs too small for writing. To test this hypothesis, we constructed and tested 20 lithium battery coin cells (10 control, 10 pencil graphite-based cells). We focused on evaluating cell charge and discharge properties through a battery tester. Results of the testing showed that pencil graphite cells had a first charge capacity of 397.3 mAh/g on average, a poor coulombic efficiency of around 52%, and low-rate capability compared to the control group. Past research reveals that up to 25% of a pencil is composed of non-graphite elements, likely a major source for poor efficiency rate capability. To overcome this obstacle, we applied prelithiation to pencil graphite anode via lithium metal in a Swagelok half cell, resulting in improved efficiency and better cycle life than control in a full cell built with LiFePO₄ cathode. These results implied that pencil graphite could not be used as a drop-in replacement for battery-grade graphite, but prelithiation treatment could make it a viable material for lithium-ion batteries.