[en] Highlights: • The first example of heterogeneous electrocatalysis based on double activation is presented. • Introduction of a secondary organic catalyst to a primary inorganic catalyst improved ORR activity. • The secondary organic catalyst donated its electron to oxygen molecule to form O₂^δ-. • Also, the secondary organic catalyst donated its proton to the single oxygen intermediate (*O). Synergistic effects of dual homogeneous catalysts for chemical reactions have been reported. Double activation (chemical transformation process where both catalysts work in concert to activate reactants or intermediates) was often responsible for the synergistic effects of dual catalyst systems. Herein, we demonstrate the extension of the double activation from chemo-catalysis to electrocatalysis. The activity of low-cost cobalt oxide electrocatalysts for oxygen reduction reaction (ORR) was significantly improved by introducing secondary-amine-conjugated polymers (HN-CPs) as the secondary promoting electrocatalyst (shortly, promoter). It was proposed that HN-CPs activated neutral diatomic oxygen to partially charged species (O₂^δ-) in the initial oxygen adsorption step of ORR. Electron donation number of HN-CP to diatomic oxygen (δ in O₂^δ-) well described the order of activity improvement, i.e., polypyrrole (pPy) > polyaniline (pAni) > polyindole (pInd). The maximum overpotential gain at ~150 mV was achieved by using pPy with the highest δ. Also, it was confirmed that proton of HN-CP was transferred to single oxygen intermediate (*O) of ORR.

[en] Keeping both the chemical and physical state of the electrode-electrolyte interface intact is one of the greatest challenges in achieving solid-state batteries (SSBs) with longer cycle lives. Herein, the use of organic electrolyte additives in the cathode electrolyte interphase (CEI) layer to mitigate the intertwined chemical and mechanical degradation in sulfide-based SSBs is demonstrated. Lithium difluorobis(oxalato)phosphate (LiDFBOP) and argyrodite (Li${}_6$PS${}_5$Cl) are used as a model system, with the LiDFBOP-derived CEI layer induced by irreversible oxidation above 4.12 V (vs Li${}^{+}$/Li) during the formation cycle exhibiting dual functions. This CEI layer retards the rate of chemical degradation between the cathode active particles and solid electrolytes at high charging potential and helps maintain intimate physical contact even at a low stack pressure of 0.75 MPa. The improved physical contact enables delivery of a high initial capacity, while chemical stability suppressing the sulfite or sulfate formation has a more dominant effect on the long-term cycle stability. This study presents a new perspective and strategies for designing cathode coating materials for sulfide-based SSBs beyond the typically used inorganic oxide materials. (© 2023 The Authors. Advanced Energy Materials published by Wiley‐VCH GmbH)