The safety design of systems using lithium-ion batteries (LIBs) as power sources, such as electric vehicles, cell phones, and laptops, is difficult due to the strong multiphysical coupling effects among mechanics, electrochemistry and thermal. An efficient and accurate computational model is needed to understand the safety mechanism of LIBs and thus facilitate fast safety design. In this work, a detailed mechanical model describing the mechanical deformation and predicting the short-circuit onset of commercially available 18650 cylindrical battery with a nickel cobalt aluminum oxide (NCA) system is established for the first time. The mechanical properties of anode, cathode, and separator are characterized. Based on the experiment results, the constitutive models of component materials are established and validated through numerical simulations. A detailed computational model including all components (i.e., separator, anode, cathode, winding, and battery casing) is then developed by evaluating four typical mechanical-loading conditions. Short-circuit criteria are subsequently established based on the separator failure, thereby enabling the mechanical model to predict the short circuit electrochemically. Results show that the model can describe LIB behaviors from mechanical deformation to internal short circuit. Results provide a powerful tool for the safety design of LIBs and related engineering systems.