Journal of Power Sources, Vol.101, No.1, 96-102, 2001
A study on the irreversible capacity of initial doping/undoping of lithium into carbon
The initial irreversible capacity, Q(i), is one of the parameters to express the material balancing of the cathode to anode in lithium-ion cells. In this work, a new terms are introduced, namely, the initial intercalation Ah efficiency (IIE) and the initial irreversible specific capacity at the surface (Q(is)), to express precisely the irreversibility of an electrode/electrolyte system. The terms depend on the active-materials and composition of the electrode, but do not change with charging state. Mesophase carbon microbeads (MPCF) have the highest value of IIE and the lowest value of Q(is) in 1 M LipF(6)/ethylene carbonate (EC) + diethyl carbonate (DEC) (1:1 volume ratio) electrolyte. The IIE value of a LiCoO2 electrode is 97-98%, although the preparation conditions of the material and the electrolyte are different. The Q(is) value of LiCoO2 is 0-1 mAh g(-1). The MPCF-LiCoO2 cell system has the lowest latent capacity. The Q(is) value increases slightly on adding conductive material. The IIE and Q(is) values vary with the electrolyte. By introducing propylene carbonate to the EC + DEC mixed solvent, the IIE values are retained, but Q(is) is increased. With the addition of methyl propionate, the IIE value is increased, and the Q(is) value is also increased slightly.
Keywords:carbon;initial irreversible capacity;initial intercalation Ah efficiency;initial irreversible;specific capacity;latent capacity