Li-O₂ batteries represent a promising rechargeable battery candidate to answer the energy challenges our world is facing, thanks to their ultrahigh theoretical energy density. However, the poor cycling stability of the Li-O₂ system and, overall, important safety issues due to the formation of Li dendrites, combined with the use of organic liquid electrolytes and O₂ cross-over, inhibit their practical applications. As a solution to these various issues, we propose a composite gel polymer electrolyte consisting of a highly cross-linked polymer matrix, containing a dextrin-based nanosponge and activated with a liquid electrolyte. The polymer matrix, easily obtained by thermally activated one pot free radical polymerization in bulk, allows to limit dendrite nucleation and growth thanks to its cross-linked structure. At the same time, the nanosponge limits the O₂ cross-over and avoids the formation of crystalline domains in the polymer matrix, which, combined with the liquid electrolyte, allows a good ionic conductivity at room temperature. Such a composite gel polymer electrolyte, tested in a cell containing Li metal as anode and a simple commercial gas diffusion layer, without any catalyst, as cathode demonstrates a full capacity of 5.05 mAh cm⁻² as well as improved reversibility upon cycling, compared to a cell containing liquid electrolyte.

The improvements in future-generation lithium-ion batteries cannot be exclusively focused on the performance. Other aspects, such as costs, processes, and environmental sustainability, must be considered. Research and development of new active materials allow some fundamental aspects of the batteries to be increased, such as power and energy density. However, one of the main future challenges is the improvement of the batteries’ electrochemical performance by using “non-active” materials (binder, current collector, separators) with a lower cost, lower environmental impact, and easier recycling procedure. Focusing on the binder, the main goal is to replace the current fluorinated compounds with water-soluble materials. Starting from these considerations, in this study we evaluate, for the first time, tragacanth gum (TG) as a suitable aqueous binder for the manufacturing process of a cobalt-free, high-voltage lithium nickel manganese oxide (LNMO) cathode. TG-based LNMO cathodes with a low binder content (3 wt%) exhibited good thermal and mechanical properties, showing remarkably high cycling stability with 60% capacity retention after more than 500 cycles at 1 C and an outstanding rate capability of 72 mAh g⁻¹ at 15 C. In addition to the excellent electrochemical features, tragacanth gum also showed excellent recycling and recovery properties, making this polysaccharide a suitable and sustainable binder for next-generation lithium-ion batteries.

Actual market requirements for storage systems highlight the limits of graphite as an anode for Li-ion batteries. Lithium metal can represent a suitable alternative to graphite due to its high theoretical specific capacity (about 3860 mAh g⁻¹) and low negative redox potential. However, several aging mechanisms, such as dendrite growth, lithium loss and the formation of an unstable SEI, decrease the performances of Li-based batteries. A suitable strategy to better understand and study these mechanisms could be the development of an electrochemical model that forecasts the aging behaviour of a lithium-metal battery. In this work, a P2D aging electrochemical model for an Li-based cell was developed. The main innovation is represented by the combination of two aspects: the substitution of graphite with metallic lithium as an anode and the implementation of SEI growth on the metallic lithium surface. The calibration of the model, based on experimental measurements and the successive validation, led to us obtaining a good accuracy between the simulated and experimental curves. This good accuracy makes the developed P2D aging model a versatile and suitable approach for further investigations on Li-based batteries considering all the aging phenomena involved.

Developing efficient electrocatalysts for oxygen reduction reaction (ORR) is fundamental to bring the Li-O2 technology closer to practical applications. However, the majority of studied catalysts for this application are either precious metals or cobalt based, which represents an obstacle for a larger scale development, both from an economical and a political point of view. In this work a simple, fully sustainable, and economic synthesis process is used to in situ nucleate SnO2 nanoparticles on the surface of commercial carbon black (C45) by taking advantage of its numerous nucleation sites to deposit and chemically anchor SnO2 nanoparticles. Such synthesis can easily be carried out through wet impregnation, without any acid treatment or high temperature process. The obtained composite material shows an optimal ORR activity, which is confirmed in Li-O2 cells. Indeed, compared to pure C45 air-cathodes, the composite cathodes lead to the formation of much more reversible film-like discharge products, allowing for reduced overvoltage and therefore improved cycling performances both at the high current density of 0.5 mA cm-2 with more than 70 cycles and in prolonged discharge/charge conditions with over 1250 h of operation at the fixed capacity of 2.5 mAh cm-2.