In Search of the Best Solid Electrolyte-Layered Oxide Pairing for Assembling Practical All-Solid-State Batteries

Abstract

All-solid-state batteries (ASSBs) are the subject of large enthusiasm as they could boost by 50% the energy density of today's Li-ion batteries provided that several fundamental/practical roadblocks can be solved.Focusing on the interface between the solid electrolyte and cathode active material (CAM), we herein studied the chemical/electrochemical compatibility of coated-layered oxide LiNi0.6Mn0.2Co0.2O2 with the three main inorganic electrolytes contenders, these being lithium thiophosphate (β-Li3PS4), argyrodite (Li6PS5Cl), and halide (Li3InCl6). Such electrolytes were prepared by either solvent-free or solution chemistry and paired with the CAM to form a composite which was further tested by assembling solid-state batteries using Li0.5In as negative electrode. Amongst the electrolytes prepared by dry routes, the best performing was found to be Li6PS5Cl followed by β-Li3PS4 and lastly Li3InCl6. In contrast, no general trend of benefit or detriment was observed when switching to solution route as it resulted in either performance improvement or deterioration depending on the electrolyte. Additionally, we show a strong dependence of the battery performance upon the presence of carbon additives. Lastly, we unraveled a pronounced chemical/electrochemical incompatibility of Li3InCl6 towards Li6PS5Cl and β-Li3PS4, hence questioning the design of hetero-structural cell architectures. Altogether, we hope these findings to provide guidance in the proper pairing of electrode-electrolytes components for designing highly performing solid-state batteries.

Visualizing the Chemical Incompatibility of Halide and Sulfide‐Based Electrolytes in Solid‐State Batteries

“…[ 45 ] In comparison, halide‐based cells usually show lower initial capacity values. For example, a carbon‐containing LiNi 0.6 Co 0.2 Mn 0.2 O 2 ‐ and Li 3 InCl 6 ‐based composite cathode has shown an initial charge capacity of 166 mAh g −1 , [ 34 ] whereas a LiNi 0.85 Co 0.1 Mn 0.05 O 2 ‐ and Li 3 InCl 6 ‐based composite exhibited an initial charge capacity slightly under 200 mAh g −1 . [ 33 ] The general shape of the charge/discharge curves is similar for all setups and is characteristic for the CAM.…”

“…[ 33 ] The high resistance and particularly the increase upon cell cycling appears to be caused by the recently reported chemical incompatibility between Li 3 InCl 6 and Li 6 PS 5 Cl, which results in the formation of an interphase and thus to a higher resistance (see discussion section below). [ 34,35 ]…”

Prospects of halide-based all-solid-state batteries: From material design to practical application

“…Janek et al ( 85 ) recently demonstrated that the interfacial ion transport resistance between sulfide and halide SSEs is negligible. In contrary, Tarascon et al ( 87 ) reported that halides are incompatible with sulfide SSEs (e.g., Li 6 PS 5 Cl and β-Li 3 PS 4 ). More detailed studies are still required to understand the heterointerface between halide and sulfide SSEs.…”

Different interfacial reactivity of lithium metal chloride electrolytes with high voltage cathodes determines solid-state battery performance

“…The 2-fold increase in R bulk of the LIC-based cells might arise from more extensive side reactions between LIC and Li 5.5 PS 4.5 Cl 1.5 , as recently reported. 44 However, the growth in bulk resistance by 25 O cm 2 increases ohmic polarization of those cells only by B7 mV at the given current density of 0.28 mA cm À2 , which will have an insignificant effect on the capacity.…”