Online monitoring of the gases evolving in Lithium ion batteries with a Multiplex-GCMS-FTIR can determine the state of all cell components. Relevant parameters like voltage, charge and discharge current and age of the cell can be controlled and varied. Thus, potential dangers from emitted gases can be gauged and their toxicity determined. This significantly eases evaluation of solutions for recycling, disposal, and second life applications. It also contributes to safer battery systems. In sum, these results lead to lower lifetime cost and enable safe implementation of future active materials, which lead to higher energy densities.