Specific surface-area measurement of lithium anode in rechargeable lithium cells

This paper reports the first successful measurement of the specific surface-area of a lithium metal anode by employing the BET method under optimum experimental conditions. The test cell used here is an AA-size cylindrical cell with a lithium anode and an amorphous-V2O5–P2O5 cathode. The experimental results clearly reveal that the lithium surface-area increases after a low-rate discharge cycle. For example, the specific surface-area of a lithium at a low-rate discharge current density of 0.2 mA cm−2 is 26 m2 g−1 which is twice that at a high-rate discharge current of 3 mA cm−2. The influence of the discharge depth on the lithium surface-area is also examined. The surface-area measurement method described here will be useful in terms of finding a way to improve both the cycle life and safety of rechargeable, lithium-metal cells.