Differential Voltage Analysis (DVA) is a commonly used method for investigating electrochemical processes, particularly at the electrode interfaces of batteries. It is especially useful for analysing phenomena such as phase transitions and intercalation processes within lithium-ion batteries. The successful use of DVA in studies of lithium-ion batteries raises the question of whether the method can also be applied to other battery technologies, e.g. lithium-sulfur (Li-S) batteries. The Li-S battery is a promising battery technology because it has a potential higher theoretical energy density (~2,500 Wh kg-1) than the lithium-ion battery technology (400 – <800 Wh kg-1). Nevertheless, the Li-S battery has the disadvantage that it suffers a significant loss of capacity after just a few charging cycles, which limits its applicability in most cases. However, improved cycle stability would significantly increase the potential of this technology. This requires a comprehensive understanding of how Li-S batteries work. Especially the interaction between sulfur and lithium-ions during operation is not yet completely understood. But there is agreement about the fact that multiple transformations occur. In the first discharge stage the solid rhombic sulfur (S8) is reduced, causing it to dissolve in the electrolyte and combine with two lithium ions to form long-chain lithium polysulfides (S8-- + 2Li+ = Li2S8). As the discharge proceeds, further chemical reactions occur in which the long-chain polysulfides are further transformed with lithium-ions to form shorter polysulfides (Li2S6, Li2S4, Li2S2). At very low states of charge, the reactions finally lead to the formation of monosulfides (Li2S), which have a low solubility and precipitate. However, the location of the precipitation cannot be predicted; it is even possible that the dissolved molecules travel through the electrolyte to the anode and settle there after precipitation. This process is known as the shuttle effect. This effect reduces the battery capacity, as the Li2S molecule is no longer converted back into S8 during the charging process. In addition, parts of the anode can be blocked by the monosulfides and will no longer participate in chemical reactions. The conversion processes from S8 to Li2S and vice versa are therefore of central importance for the service life of a Li-S battery and require detailed investigation. At this point, the DVA may be able to provide helpful informations. The differential voltage (DV) is the derivative of the voltage U in relation to the charge quantity Q: DV = dU / dQ. That means the DV curve represents the slope of the voltage as a function of the amount of charge that has been removed. The peaks in the DV curve indicate that phase transitions are taking place. In the case of lithium-sulphur batteries, this is the shortening of polysulphide chains. This makes it possible to show, for example, at which states of charge a particularly large amount of shortening occurs. It is noticeable that several maxima can be observed at high states of charge, while no further phase transitions appear to occur over an extended range of the state of charge (SOC). This indicates that the rhombic sulphur is almost completely reduced at the beginning of the discharge. The dissolved sulfur anions then interact with the lithium cations and after a short time the long-chained polysulfides Li2S8 are shortened to Li2S6 and Li2S4. At this moment, around a quarter of the total capacity has been removed from the battery. In the next discharge stage, the voltage gradient is close to zero for a longer period. So, the transformation from Li2S4 to Li2S2 and finally to Li2S happens very slowly. The aging of the Li-S battery results in a change in the DV curve. One possibility is that the curve is compressed by loss of capacity. If the individual discharge phases are compressed to the same extent, it is reasonable to assume that there are generally fewer reactants present. This can happen, for example, if the anode is blocked by the shuttle effect. It is also conceivable that fewer maxima occur or some are less dominant than before. Also, there may be a change in the shape of the peaks, e.g. from high peaks to flat plateaus. In this study, lithium-sulfur cells were constructed in a full cell configuration (PAT-cell) with a polymer-based solid electrolyte. Graphite was added to the cathode to enable the electrical conductivity. The cells first underwent a forming process in which they were fully discharged. They were then aged over a period of 50 cycles. After 10, 30 and 50 cycles, a differential voltage analysis (DVA) was carried out. Cycling was performed at a C-rate of C/10 between 100 % SOC and 0 % SOC. The forming process and the DVA each were carried out with a C-rate of C/50. The specified C-rates refer to the determined theoretical capacity in each case. During the entire experiment, the cells were stored at 50°C in a temperature cabinet. Three different electrolyte thicknesses and three different electrolyte compositions were investigated. For each pair (thickness + composition) three cells were constructed.