Effect of graphite shape on tortuosity and rate capability of electrodes

Mixing spherical natural graphite with flaked artificial graphite improves the performance of lithium-ion batteries. However, the latter increases the viscosity of the electrode slurry and reduces the coating properties. The present study compares electrodes with different sizes and proportions of flaked artificial graphite. In addition, the effects of flaked artificial graphite on the rheological properties of slurries, the structure of electrodes, and the battery performance of electrodes are discussed. The small addition of flaked graphite to spherical natural graphite has been demonstrated to result in a deterioration of coating properties and a decrease in ionic diffusion, which is attributable to an increase in tortuosity. However, this process has been demonstrated to concomitantly increase the electrode–electrolyte interfacial area and decrease reaction and electrical resistance. Collectively, these phenomena enhance the C-rate characteristics of electrodes. In addition, the electrodes exhibit enhanced peel strength and elevated C-rate characteristics, particularly when the spherical natural graphite and flaked artificial graphite have comparable dimensions, despite the inferior coating properties.