The stability of the electrode-electrolyte interface and its defects can result in lithium metal dendrite initiation and propagation through the electrolyte when the battery is in use. This phenomenon is a key issue that can change battery properties and lead to short circuit. The morphology and dynamic of dendrites growth can be different depending on the system electrode-electrolyte and relies on a coupled multiphysics phenomenon [1] involving electro-chemical phase change that is influence by mechanics in solid state batteries [2]. To model these phenomena a phase field model has been implemented to investigate the potentiality of the approach for dendritic growth prediction using the multiphysics finite element software Freefem++ (see https://freefem.org/). The solving of the system involving four conservation equations is performed sequentially using an iterative approach and convergence criterions. The phase field model is considered to represent the formation of lithium metal dendrites from lithium ions. The lithium ions transport involving both diffusion and migration is another conservation equation considered herein and solved before the electrical conduction in the electrolyte. The mechanical equilibrium is then solved to compute the stress state that influence the dendrite formation. The dendrite formation influences the electrolyte mechanical, electrical and related to transport properties leading to a highly coupled system. The results shown herein demonstrate the potential of the prototype to model the onset and growth of lithium metal dendrites in battery and illustrate coupled behaviour of solid state batteries electrolytes and the observed tendencies that mechanical confinement influence dendrite formation. REFERENCES [1] Liu, Yuan et al., Unlocking the Failure Mechanism of Solid State Lithium Metal Batteries, Adv. Energ. Mat., DOI: 10.1038/s41467-021-27311-7, (2021). [2] Tantratian, Karnpiwat et al., Unraveling the Li Penetration Mechanism in Polycrystalline Solid Electrolytes, Advanced Energy Materials, DOI: 10.1002/aenm.202003417, (2021).