A LiCoPO₄-based high-voltage lithium-ion battery was fabricated in the format of a 1.2 Ah pouch cell that exhibited a highly stable cycle life at a cut-off voltage of 4.9 V. The high-voltage stability was achieved using a Fe-Cr-Si multi-ion-substituted LiCoPO₄ cathode and lithium bis(fluorosulfonyl)imide in 1-methyl-1-propylpyrrolidinium bis(fluorosulfony)imide as the electrolyte. Due to the improved electrochemical stability at high voltage, the cell exhibited a stable capacity retention of 91% after 290 cycles without any gas evolution related to electrolyte decomposition at high voltage. In addition to improved cycling stability, the nominal 5 V LiCoPO₄ pouch cell also exhibited excellent safety performance during a nail penetration safety test compared with a state-of-the-art lithium ion battery. Meanwhile, the thermal stabilities of the 1.2 Ah pouch cell as well as the delithiated LiCoPO₄ were also studied by accelerating rate calorimetry (ARC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and in situ X-ray diffraction (XRD) analyses and reported.

Advanced lithium-ion batteries are under development, but they still suffer from safety issues. Solid state batteries present a good solution as they are safer than lithium-ion ones and they can respond to the high energy need for the electromobility. A huge effort is applied to batteries with sulfide ceramic electrolytes due to their high ionic conductivity at room temperature. But the use of this electrolyte results in some challenges such as the incompatibility with high voltage positive material, the incompatibility with lithium metal, the H₂S generation, ... Since a few years, Hydro Québec has made research on solid state batteries and particularly on batteries with sulfide ceramic electrolytes. An innovative solution was developed to manage the interfacial incompatibility of sulfide with LiNi_xMn_yCo_zO₂ material. A protective layer was obtained on sulfide particles. In solid state batteries, the contact between particles in the positive electrodes must be maintained all along the cycling. For this reason, a specific binder was designed to maintain a good contact upon cycling of NMC 622. Several configurations were considered and compared to standard binder to find the best configuration. This solution can be adjusted to NMC with higher Ni content that suffer from a higher volumetric change at high end of charge voltage due to structural changes. Lots of patents were made by Hydro Québec on this technology to address a solution to each challenge related to sulfide ceramic electrolytes. This presentation will focus on the development of a positive electrode that faced all challenges given by sulfide ceramic electrolytes and more particularly on the binder developed for this technology. Performances obtained in pouch cells with optimized positive electrodes will be also presented.

Solid-state batteries are expected to provide holistic solutions to overcome major growth barriers in the EV market, with its higher energy density, faster charging rate, intrinsic safety, and potentially better affordability. Sulfide-based electrolyte is attracting extensive interest among other solid electrolyte chemistries, owing to its outstanding conductivity and processibility at ambient temperature. According to multiple announcements from battery manufacturers and OEMs, the sulfide-based all-solid-state batteries are believed to be only a few years away from its start of production for EV applications. As demonstrated in literature, the sulfide solid electrolyte is not stable with lithium metal. To be competitive with other technologies, the sulfide solid electrolyte could be combined with lithium metal, and the obtained all-solid-state batteries demonstrate comparable performances at high c-rate. But the dendrite formation or cracks are observed, even if high pressure is applied. This presentation will address the remaining challenges of sulfide-electrolyte film and interfaces with lithium metal. The development of new “binders” for sulfide film electrolyte will be presented with the demonstration of relationship of solid electrolyte ceramic film composition, binder, density, flexibility to offer high conductivity and easily manipulation. With stabilized lithium metal interface and specific properties of solid electrolyte film by binder development, more than 700 cycles under industry-relevant pressure conditions at moderate temperature under pouch-cell configuration were obtained. The complementarity between binder properties, mixing, preparation and electrochemical measurements will be explained with technical and economical issues to bring the technology closer to the market.

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. Solid oxide or sulfide are largely studied to allow the emergence of all-solid-state batterie based on solid electrolyte ceramic. In particular, the sulfide-based solid electrolytes possess favorable mechanical properties and low temperature synthesis compared to oxide, high ionic conductivity comparable to liquid electrolytes but suffer of moisture exposure that could induce H₂S generation and very expensive precursor. Sulfide-based solid-electrolytes can potentially be employed in conjunction with a lithium metal negative electrode and 5V-class high voltage positive electrode material. Different families of sulfide electrolyte as glass ceramic, thio-LISICON, LGPS, argyrodites are synthesized by similar precursor as Li₂S-P₂S₅ and other components in function of composition. Among these families, argyrodites are promising due to their high ionic conductivity and no rare element. However, there are still several issues to overcome with argyrodite: reactivity with lithium metal and positive electrolyte material (active material, electronic conductor, binder, current collector...), moisture stability and use of expensive and unsafe Li₂S. O-doped argyrodites are known strategy to enhance stability against cathode material, lithium metal and moisture stability. In this field and since a few years, Hydro-Quebec has decided to conduct specific research on all-solid ceramic batteries and especially in the field of sulfide-based ceramic electrolytes. We develop the synthesis of argyrodite type oxysulfide with one-step ball milling process. We use a low-cost oxygen precursor (Li₂SO₄) to partially substitute Li₂S. A specific study has been carried out to (1) optimize the composition of sulfide solid electrolyte to lower the cost and maintain or increase the properties as ionic conductivity, electrochemical and moisture stability, (2) better understand the reactivity at various dewpoints, (3) evaluated the stability in dry room. The complementarity between synthesis process, compositions, NMR analyses, XRD analyses, Raman’s analysis, ionic conductivity, electrochemical stability, and safety measurements will be presented on sulfides prepared at Hydro-Quebec.

All-solid-state batteries are known to be the new energy storage holy grail that will lead to safer batteries with higher energy density than current Li-ion batteries. The use of a solid electrolyte enables the use of lithium metal as the anode material. However, its composition, its thickness, and the quality/nature of its passivation layer can strongly affect the performance of the battery. For this reason, we propose a simple benchmarking method that evaluates and compares the quality and electrochemical performance of various Li anodes. This method can be easily reproduced, especially concerning the electrochemical evaluation that uses a commercial liquid electrolyte and the widely spread coin-cell format. In total, ~285 coin cells were assembled to benchmark our in-house lithium metal foil (Lithium HQ) with two commercial ones and the results showed the superior performance of our Li metal anode. The performance of the cells seems closely related to the quality and uniformity of the Li surface. In addition, we propose including in the benchmarking method the effect of Li aging in a dry room on the electrochemical performance. This effect is important to consider because the fabrication of all-solid-state batteries is conducted in such an environment.