The development of highly efficient batteries is a critical need in the automotive industry in order to enable the future success of Electric Vehicles (EV). The optimization of battery stacks integration in EV can greatly benefit from an improvement of Li-ion cells modular assembly and electrical interconnection, while ensuring a high level of safety. This is part of the technical challenges of the European SPICY project. In this paper, we present a new polymer-based packaging concept for Li-ion cells. A modular approach is investigated in order to enable a high flexibility in the selection of power output and stack geometry. The design of the polymer packaging is described in details. In addition to the Li-ion cells and USB power bank packaging, a specific connector for packaging assembly is developed. The manufacturing of the initial prototypes by 3Dprinting and demonstrators by injection moulding is described.