All-Solid State Lithium-Sulfur Batteries

Currently, lithium-ion batteries incorporated in electric vehicles do not allow to store enough energy to ensure sufficient autonomy. Therefore, it’s necessary to develop new generations of batteries with higher energy density. Among battery technologies, the lithium-sulfur system (Li-S) is considered to be one of the most promising solutions due to a theoretical energy density of 2500 Wh/kg. However, its lifetime remains limited due to the polysulfide shuttle effect, induced by the use of liquid electrolyte. Indeed, many polysulfides (noted Li 2 S x 1 ≤ x ≤ 8), formed during the sulfur reduction to Li 2 S, dissolve in liquid electrolyte and diffuse between both electrodes, leading to a rapid decrease of electrochemical performances. All-solid-state Li-S batteries were studied in order to bypass the limitations of liquid electrolyte. The electrode is a composite material with sulfur (S 8 ) as active material, argyrodite (Li 6 PS 5 Cl) as solid electrolyte for ionic conduction and Ketjen Black (KB) as additive conductor for electronic percolation. The liquid electrolyte between both electrodes is replaced by the solid electrolyte used in the composite electrode and metallic lithium is used as negative electrode. /sub>S x 1 ≤ x ≤ 8), formed during the sulfur reduction to Li 2 S, dissolve in liquid electrolyte and diffuse between both electrodes, leading to a rapid decrease of electrochemical performances. The positive electrode was prepared by mixing and ball-milling at 370 rpm for 5h using a high-energy planetary ball mill, S 8 , Li 6 PS 5 Cl and KB with a weight ratio of 25:50:25. The battery displays a reversible capacity of 1565 mAh/g after 10 cycles at a current density of 134 µA/cm² (corresponding to a rate of C/10) with an initial discharge capacity of 1230 mAh/g and an extra capacity of around 335 mAh/g, observed for the first time and currently under studies. 8), formed during the sulfur reduction to Li 2 S, dissolve in liquid electrolyte and diffuse between both electrodes, leading to a rapid decrease of electrochemical performances. At high current density, with lithium negative electrode, we observed strange potential decreases that can be related to short circuit phenomena. One explanation for short circuit phenomena can be the formation of lithium dendrites, although they are not supposed to grow in solid electrolyte. The presence of dendrites will be evidenced by solid state NMR. Using alternative Li-In electrode, this phenomenon was totally suppressed. In this presentation, we will then show our best optimized solid state batteries using a Li-Indium electrode with a good capacity (1660 mAh/g after 10 cycles at C/10), a good coulombic efficiency and a reasonable polarization for a solid-state battery and at room temperature. Perspectives in term of energy density and industrialization (upscale of the lithium ion conductors) will be presented.