Rational Optimization of Cathode Composites for Sulfide-Based All-Solid-State Batteries

Abstract

All-solid-state lithium-ion batteries with argyrodite solid electrolytes have been developed to attain high conductivities of 10−3 S cm−1 in studies aiming at fast ionic conductivity of electrolytes. However, no matter how high the ionic conductivity of the electrolyte, the design of the cathode composite is often the bottleneck for high performance. Thus, optimization of the composite cathode formulation is of utmost importance. Unfortunately, many reports limit their studies to only a few parameters of the whole electrode formulation. In addition, different measurement setups and testing conditions employed for all-solid-state batteries make a comparison of results from mutually independent studies quite difficult. Therefore, a detailed investigation on different key parameters for preparation of cathodes employed in all-solid-state batteries is presented here. Employing a rational approach for optimization of composite cathodes using solid sulfide electrolytes elucidated the influence of different parameters on the cycling performance. First, powder electrodes made without binders are investigated to optimize several parameters, including the active materials’ particle morphology, the nature and amount of the conductive additive, the particle size of the solid electrolyte, as well as the active material-to-solid electrolyte ratio. Finally, cast electrodes are examined to determine the influence of a binder on cycling performance.

New Insights of Infiltration Process of Argyrodite Li6PS5Cl Solid Electrolyte into Conventional Lithium-Ion Electrodes for Solid-State Batteries

“…It should be noted that the infiltration of the LPSC electrolyte into conventional lithium-ion battery NCM electrodes leads to poor electrochemical performance due to the formation of plate-like LPSC particles, the complicated infiltration process, and the fact that infiltrated LPSC electrolytes are working as an insulating layer (Figure 9). At the same time, non-infiltrated conventional LIB NCM electrodes exhibit extremely low performance due to sluggish lithium kinetics when compared to cells with all-solid-state battery components [26]. Based on the obtained results, we proposed a mechanism for the infiltration process of the solid electrolyte into the cathode composite with various values of porosity, as shown in Figures 7 and 9.…”

“…Electrochemical testing of the infiltrated cathode-For electrochemical tests, a lithium metal anode (MTI, Li chips, diameter of 15.6 mm, thickness of 0.25 mm) was used as a counter electrode. The method used to prepare the lithium metal anode is described in [26]. To prepare the bilayers, 320 mg of electrolyte powder is placed in a Ø16 mm pellet die and pressed at 50 MPa for a few seconds.…”

“…However, comparing oxide-and sulfide-type electrolytes shows that while the oxide electrolyte has excellent chemical and electrochemical stabilities, its processability is poorer. Sulfide-based electrolytes, on the other hand, have made significant progress in dry-and wet-chemistry production of the cathode and electrolyte films [24][25][26].…”

Film Processing of Li6ps5cl Electrolyte Using Different Binders and Their Combinations

“…For samples using NBR and HNBR, however, an additional semi- circle is observed in the Nyquist plots, indicating an additional contribution to the overall impedance of the electrolyte films, which leads to far lower ionic conductivities obtained for samples using these binders. Nevertheless, a recent study showed that stable cycling of NMC811 cells is still possible, even with electrolyte films incorporating 3 wt% of NBR [27]. In order to prepare even thinner samples, the Li 6 PS 5 Cl material needs to be crushed by e.g.…”

Conductivity of cold sintered diphasic composites containing a ceramic active material and a solid-state electrolyte or carbon for all solid-state batteries

“…[17][18][19][20][21] The fabrication of these batteries is relatively simple given the ductile nature of polymer solid electrolytes, but the thermal/mechanical stability, ionic conductivity, and transference number of these materials are generally poor. 22,23 An alternative route is the use of so inorganic solid electrolyte materials, such as glasses based on the Li-P-S ternary system, 24,25 which allow for the fabrication of multilayered 26,27 and composite electrodes [28][29][30][31][32][33] at low temperatures/pressures. These glassy materials, however, oen suffer from ambient atmosphere instability and a limited electrochemical stability window.…”