The main components and, most notably, the concentration of the non-aqueous electrolyte solution have not significantly changed since the commercialization of Li-ion batteries in the early 1990s. However, the quest for electrochemical energy storage systems with high-energy content has driven researchers to reconsider the suitability of the “standard” one molar concentration and look toward highly concentrated electrolyte solutions. However, the interplay between the fundamental electrolyte properties and the cell performance is not consistent with what would be expected based only on the electrolyte ionic conductivity. Here, the recent progress and future perspectives on the correlation between the physicochemical properties of non-standard electrolyte solutions and their ability to improve the energy storage performances of lithium-based batteries are discussed.