Mathematical modeling of the lithium deposition overcharge reaction in lithium-ion batteries using carbon-based negative electrodes

The processes that lead to capacity fading affect severely the cycle life a nd rate behavior of lithium-ion cells. One such process is the overcharge o f the negative electrode causing lithium deposition, which can lead to capa city losses including a loss of active lithium and electrolyte and represen ts a potential safety hazard. A mathematical model is presented to predict lithium deposition on the negative electrode under a variety of operating c onditions. The Li(x)C6\1 M LiPF6, 2:1 ethylene carbonate/dimethyl carbonate , poly(vinylidene fluoride-hexalfuoropropylene) \LiMn2O4 cell is simulated to investigate the influence of lithium deposition on the charging behavior of intercalation electrodes. The model is used to study the effect of key design parameters (particle size, electrode thickness, and mass ratio) on t he lithium deposition overcharge reaction. The model predictions are compar ed for coke and gaphite-based negative electrodes. The cycling behavior of these cells is simulated before and after overcharge to understand the effe ct of overcharge on extended cycling. These results can be used to establis h operational and design limits within which safety hazards and capacity fa de problems, inherent in these cells, can be minimized. (C) 1999 The Electr ochemical Society. S0013-4651(99)01-088-5. All rights reserved.