Quantification of reversible and irreversible lithium in practical lithium-metal batteries

Accurate assessment of the reversibility of electrodes is crucial for battery performance evaluations. However, it is challenging to acquire the true reversibility of the Li anode in lithium-metal batteries, mainly because an excessive amount of Li is commonly used. Here we propose an analytic approach to quantitatively evaluate the reversibility of practical lithium-metal batteries. We identify key parameters that govern the anode reversibility and subsequently establish their relationship with the cycle number by considering the mass of active and inactive Li of the cycled Li anode. Using this method, we show that the mass of active Li can be quantitatively distinguished from the mass of inactive Li of the cycled anodes in Amp hour-level pouch cells. This work opens an avenue for accurately assessing degradation and failure in lithium-metal batteries. An accurate evaluation of lithium-metal battery performance is challenging due to the excessive lithium that is often used at the anode. Here the authors report a methodology to assess the degradation mechanism and cycle life of practical lithium-metal batteries.