Methodology and Electrochemical Techniques for Development of All-Solid-State Batteries

Abstract

Despite some progress performed, state-of-the-art lithium ion batteries still require improvements in energy and power to extend the range of electric vehicles and reduce charging time. In this domain, all-solid-state batteries are viable alternatives to conventional batteries employing organic electrolytes because of their benefits, i.e., high power density, high energy density, long-life operation and safety. These advantages stem from the great features of inorganic solid electrolytes, which are single ion conductor, so a high lithium ion transport number, and no-liquid nature. In particular, the sulfide-based solid electrolytes possess favorable mechanical properties, allowing all-solid-state batteries to be easily prepared via simple mixing and cold-pressing processes, facilitating the scale-up.Sulfide-based solid-electrolytes can potentially be employed in conjunction with a lithium metal negative electrode and 5V-class high voltage positive electrode material. Indeed, lithium metal is believed to be the most promising negative electrode due to its specific large capacity (3862 mAh.g-1), low volumetric density (0.534 g.cm-3 at 20°C) and the lowest electrochemical potential (-3.03V vs ENH). Nevertheless, like most metal, lithium metal is morphologically dynamic. Its surface morphology is modified, since during the electrochemical cycling, a part of lithium migrates to the other electrode to react and is then plating on its surface heterogeneously, leading to a volume change and sometimes dendrite growth with potential internal short circuit and life-threatening accidents. Ceramic solid electrolytes have been considered to be the ideal solution to prevent dendrite growth because of their high shear modulus and high lithium transference number. In the same time, the chemical nature and composition of ceramic solid electrolyte can affect its reactivity with lithium metal. In the same time, the electrochemical stability of solid electrolyte depending of its nature and composition is a key parameter to mix it with the different components of positive electrode as active materials and electronic conductors to ensure the better percolation and performances. The oxide–based ceramic solid electrolytes can be shaped by sintering at high temperature, leading to a grain and –grain boundary microstructure with some porosity, facilitating the lithium dendrite growth through grain boundaries. Due to the low density and plasticity of sulfide based inorganic solid electrolyte, the dendrite growth through the particle-particle contact can be reduced but still present.Hence different parameters can influence the performances and aging of all solid state ceramic battery. To explore them, various electrochemical technics and associated specific treatments can be developed to extract and identify each phenomena and ensure the better development of this technology. A specific sequential methodology will be presented with different examples from the materials, interfaces with lithium metal, pseudo-composites and temperature effects up to aging of total all-solid–state ceramic battery based on sulfide technology. The extracted different parameters and the relationship between them will be presented.