The mechanism of lithium ion insertion in LiAl alloys and in LiMnO2 layered oxide into LiAl/LiMnO2 cells has been investigated by combining data from a variety of techniques including, electrochemical techniques (cycling voltammetry, galvano–potentiostatic cycling), acoustic emission (AE) technique and XRD analyses. The aim of this study was to consider the feasibility of the AE measurements for aging characterization of lithium-ion cell. The objective was to detect and to inquire the electrochemical and structural processes which appear into the negative lithium–aluminum electrode (lithium insertion/desinsertion of lithium ions and α/β intermetallic phase transformation) and into the positive LiMnO2 electrode (volume expansion, particle fragmentation). The acoustic emission was used like a nondestructive method for monitoring of the processes, occurring inside the cell. During the cycling, the acoustic emission events were much more intensive at the discharge process and they can be attributed to the phase transformation from α(LiAl) to β(LiAl) as well as to the intercalation of lithium ions in the MnO2 to LiMnO2.