The world is entering an era where fossil fuels are no longer vital to power. The search for sustainable technologies capable of producing and storing green energy is mandatory. Batteries are the leading technology for clean energy storage. The most significant breakthrough in this field appeared with the advent of Lithium-Ion batteries (LIB). However, with the evolution of society towards an energy-dependent reality, the demand for batteries with higher energy density reduced fabrication cost, and extended cycle life creates the need for further innovation toward a technology able to surpass the LIB entirely.

The new generation of batteries will possibly replace the liquid with a solid electrolyte. Using solid-state electrolytes aims to eliminate safety concerns regarding the flammable liquid electrolytes, eliminating the formation of dendritic structures and, therefore, ensuring reliability. Additionally, solid electrolytes are expected to offer a wider electrochemical stability window and are compatible with high-potential electrodes, enabling them to achieve a higher energy density. Inorganic solid-state electrolytes can be divided into categories that summarize the characteristics of the most studied families of electrolytes, such as Li/Na-SICON, argyrodite, garnet, perovskite, and most recently, antiperovskite structures. Classifying inorganic electrolytes considering the dominant element is also possible. Sulfide and oxide electrolytes are the most studied. However, these electrolytes still face several challenges for mass production. Recently, a new class of solid electrolytes containing halogen elements has been considered an alternative to overcome these setbacks - the halide electrolytes. Here we will discuss the most promising electrolytes giving a historical perspective. We will base our reflection on the available bibliography and our own theoretical and experimental data.