An experimental method of collecting high-resolution neutron powder diffraction data in a wide angular range on permanently rotating prismatic Li-ion batteries cell, which allows to eliminate a need of complex absorption correction due to highly anisotropic attenuation paths for thermal neutrons in prismatic cells, is proposed. Neutron diffraction data, in quality enabling Rietveld refinement, was collected ex situ at discrete (predefined) cell states-of-charge (SOC = 100% and 0%). Besides this, an in operando neutron powder diffraction study on a permanently rotating prismatic cell is reported, where cell connection to potentiostat was supplied using slip ring electric contact. An excellent agreement between experimental data on prismatic and 18650-type Li-ion cells was noticed. The proposed methodology opens new experimental capabilities for in operando neutron powder diffraction studies on prismatic cells (either commercial or lab based) at different experimental conditions (state-of-charge, charging protocol, current rate, state-of-health, temperature and/or cell chemistry etc).