Impact of natural and synthetic graphite milling energy on lithium-ion electrode capacity and cycle life

Abstract

The article presents a correlation between a graphite milling energy and electrochemical performance of the Li-ion graphite electrode. Synthetic and natural graphite electrodes were examined and six different milling energy values were applied to each graphite type. For the first time, ethanol was successfully used as a liquid milling media. Results indicate a clear relationship between a milling energy, an initial capacity, and a cycle life behavior of the electrode. The high capacity and cycling stability were attributed to the ethanol presence during milling since it modified the active material surface by a partial oxidation. The ethanol-induced oxidation during a milling process promotes a more stable SEI layer formation. According to this research, we can design a simple milling process for the best graphite intercalation capacity in Li-ion cells. Energy calculations allow for an easy transfer of this technology between laboratories or large-scale commercial manufactures. To the best of our knowledge, those are the first milled graphite electrode examinations that include a high charge/discharge rate with 100 full cycles. This is also the first time that the ethanol wet-milling process is used and a general dependence of the capacity and degradation rate from the milling energy is examined.