The daily application of lithium-ion-batteries (LiB) is increasing rapidly. With the increasing number of use cases and the further strong increase in storable energy per cell, the risk of malfunctions in the use phase is also increasing. To ensure safe operation of lithium-ion batteries, it is therefore essential to know the reactions in case of thermal runaway and to test them in a safe and reproducible procedure. This research work makes a significant contribution to the understanding of external influence parameters as well as the reproducible performance of nail penetration tests. In addition, based on a reproducible testing methodology, this thesis developed an approach to predict nail penetration test results based on straight forward mathematical equations. The variation of the test parameters during the test execution enables a deeper understanding of the proceeding reactions of the thermal runaway of LiBs. If the compression of a cell between two flat plates is increased during nail penetration, a later but stronger response is shown. The voltage drop occurs in a shorter time, which increases the cell surface temperatures. In contrast, increasing the nail diameter from 2 to 5 mm does not affect a change in voltage drop, cell surface temperatures, or infrared active gas product concentrations. A change in the free active lithium ion concentrations in the anode, by variation of the State of Charge or also State of Health, causes an increase in the severity of the reactions when increased and a decrease when decreased. The measureable cell surface temperatures increase steadily as the lithium ion concentration increases, shifting the gas product concentrations from increased electrolyte evaporation (EC, EMC, DMC) to decomposition products (CO2, CO, linear hydrocarbons). A reproducible test methodology for nail penetration with low standard deviation was developed based on the determined correlations through the environmental parameter variations. In addition, with increasing importance due to increasing application, the ability to predict thermal runaway results can be considered. By applying the developed test methodology and using LiB while varying capacity (1 to 3 Ah) and cathode materials (NMC 111, NMC 622, and NCA), a mathematical description of thermal runaway effects using linear and nonlinear equations could be developed. Both direct cell parameters and indirect cell parameters are used for the description. Thus, with the developed scaling methodology, the necessary number of test for valid results can be reduced and test results of cells in the scaling range can be predicted.weiterlesen