The Role of Carbon Black in LiMn[sub 2]O[sub 4]-Based Composites as Cathodes for Rechargeable Lithium Batteries

Abstract

-based composites have been prepared by cold pressing physical mixtures of carbon black (CB), and polyvinylidenefluoride (PVDF). The PVDF content has been kept constant (ca. 14.5% by volume or 10% by weight). The and CB contents have been changed in an opposite way, i.e., from 59.6 vol % (or 90.6 wt %) to 19.2 vol % (or 49 wt %) for and from 0 vol % (or 0 wt %) to 32.2 vol % (or 38 wt %) for CB. The microstructure of the composites shows clusters formed of aggregated particles of either or CB. The electrical conductivity follows a percolating process in which the conductivity changes by five orders of magnitude, the percolation threshold being 3 vol % of CB. The first discharge capacity changes from 0 to 135 mAhg−1 for increasing the CB content. The change in capacity also seems to follow a percolation process in which the sharp increase in capacity is observed for CB contents close to 3 vol %. The discharge capacity of the -based composites is controlled by electronic transport within the composite, the electronic transport depending on the microstructure of the composite. © 2001 The Electrochemical Society. All rights reserved.