Lithium-ion batteries (LIBs) are the most widely used electrical energy storage devices in various application areas. Since aging reduces their performance, it is important to diagnose this phenomenon. Currently, the aging of LIBs is determined either by destructive methods or by methods that depend on electrical components. In our study, we were able to diagnose the state of aging of the battery using calorimetry, which requires thermal measurements. The temperature profile can be used as an indicator of the aging state. This can be considered as a simple and effective way without the need for costly and/or destructive analysis.