Differential Capacity Analysis, a Tool to Examine the Performance of Graphites for Li-Ion Cells

Abstract

Li-ion battery technology has emerged over the past few years as the prime candidate for meeting the requirements of portable, high energy density and specific capacity power sources [1–3]. Among the materials considered for the anode electrode, carbon is an attractive candidate because of its low cost, chemical stability and excellent reversibility for Li intercalation. Although the equation that describes the formation of LiC₆ is fairly simple, the real reaction is much more complex [4]. Side reactions are responsible for a “charge loss” or “irreversible specific charge” (Cirr), and is accompanied by irreversible consumption of material (lithium and electrolyte). There are several effects that is beleived to contribute to Cirr, namely the SEI formation [5], solvated Li co-intercalation, reduction of surface impurities or surface complexes, etc. The formation of the SEI pasivating layer is thought to be the major contribution to the capacity losses (Cirr). Several authors have examined in detail and correlated the Cirr in reference to the Brunauer-Emmett-Teller (BET) surface area for various carboneous materials, like cokes [3,4], graphites [4,6] and carbon blacks [7].