Temperature effect on the graphite exfoliation in propylene carbonate based electrolytes

Graphite exfoliation at a low potential has long been an issue for lithium-ion cells using a propylene carbonate (PC) based electrolyte. Two different mechanisms have been proposed in literature to explain this structural degradation. In this study, the initial lithium intercalation temperature is found to have a great impact on the extent of the graphite exfoliation. At an elevated temperature, the exfoliation can be largely suppressed and the irreversible capacity loss is reduced substantially. After the initial cycling at 50 degrees C, the graphite anode can be cycled in a PC-based electrolyte at room temperature without the exfoliation problem. It is also discovered that such a graphite anode gives rise to a specific capacity of over 372 mAh g(-1) at 50 degrees C and a room temperature capacity higher than that of a graphite anode with the initial lithium intercalation at room temperature. This finding sheds a new light on the exfoliation mechanism. It may lead to a simple cycling procedure that allows us to make rechargeable lithium-ion batteries with better safety and higher capacity. (C) 2009 Elsevier B. V. All rights reserved.