Decoupling Parasitic Reactions at the Positive Electrode Interfaces in Argyrodite-Based Systems

Abstract

Li-ion batteries are the key stones of electric vehicles, but with the emergence of solid-state Li batteries for improving autonomy and fast charging, the need for mastering the solid electrolyte (SE)/electrode material interfaces is crucial. All-solid-state-batteries (ASSBs) suffer from long-term capacity fading with enhanced decomposition reactions. So far, these reactions have not been extensively studied in Li6PS5Cl-based systems because of the complexity of overlapping degradation mechanisms. Herein, those reactions are studied in depth. We investigated their effects under various operating conditions (temperature, C-rate, voltage window), types of active materials, and with or without carbon additives. From combined resistance monitoring and impedance spectroscopy measurements, we could decouple two reactions (NMC/SE and VGCF/SE) with an inflection dependent on the cutoff potential (3.6 or 3.9 V vs Li-In/In are studied) on charge and elucidate their distinct repercussions on cycling performances. The pernicious effect of carbon additives on both the first cycle and power performances is disclosed, so as its long-term effect on capacity retention. As a mean to resolve these issues, we scrutinized the benefits of a coating layer around NMC particles to prevent high potential interactions, minimize the drastic loss of capacity observed with bare NMC, and simply propose to get rid of carbon additives. Altogether, we hope these findings provide insights and novel methodologies for designing innovative performing solid-state batteries.

Localised degradation within sulfide-based all-solid-state electrodes visualised by Raman mapping

“…A similar observation was made with Raman measurements on the LiCoO 2 and Li 6 PS 5 Cl solid–solid interface, 9 highlighting the oxidative stability of the electrolyte breakdowns when in contact with partially de-lithiated positive electrode materials. Though the negative effects of carbon additives on degradation have been frequently reported, 29,30 from this initial study no correlation of the degradation products with carbon position was observed. Mapping studies, using a variety of carbons will be probed, as well as in situ mapping investigations to further understand the origin and location of composite electrode degradation.…”

One Stone, Three Birds: An Air and Interface Stable Argyrodite Solid Electrolyte with Multifunctional Nanoshells

“…The LiF@Li 2 O‐dominated CEI protects the inner LPSC from decomposition at high current density and voltage, and its thin thickness (6–8 nm) facilitates fast ion‐electron transport through quantum tunneling, resulting in higher capacity at high rates. [ 48 ] Moreover, the crystallized components of the CEI exhibit a wide electrochemical window (e.g., LiF is 0–6.4 V), reducing the decomposition of argyrodite and ensuring intact contact under high voltage. The uniformly dispersed conductive agents and solid electrolytes enable normal operation under thick cathodes, and the excellent compatibility between LPSC‐OF 0.25 and unmodified LCO results in stable operation at high rates, high voltage, and thick cathodes.…”

An Advanced Cell for Measuring In Situ Electronic Conductivity Evolutions in All‐Solid‐State Battery Composites

“…Kinetic issues are even enhanced in all-solid-state-batteries (ASSB) using thiophosphate-based solid electrolytes (SE), since the addition of electronic conductive species such as carbon accelerates the degradation of Sbased SE. [4][5][6][7] Equally, the crucial matter of unoptimized ionic and electronic percolation-linked with particle sizes dispersion, mixing process efficiency, and materials surface properties-remains an issue, as reflected by the low first charge capacity obtained in such systems and the high polarization arising from important transport resistances. [8][9][10] In order to investigate these issues and determine kinetic parameters, traditional approaches such as impedance spectroscopy, galvanostatic or potentiostatic intermittent titration techniques, and signature curves are commonly employed.…”