In-situ construction of stable cathode/Li interfaces simultaneously via different electron density azo compounds for solid-state lithium metal batteries

The poor compatibility of the electrodes-electrolyte interfaces of rechargeable lithium metal batteries (LMBs) with solid-state electrolytes (SSEs) limit their wide applications. Herein, azo compounds as additive are firstly applied in SSEs and we propose a mechanism of regulating the cathode/anode interfaces by azo compounds with different electron groups in SSEs. Through in-situ constructing, the free radicals formed by electron-withdrawing/electron-donating group can be grafted onto different electrodes on demand, thereby forming stable interfaces at both cathode and anode sides, which effectively improves SSEs compatibility in LMBs. Consequently, superior cycling stability is demonstrated by Li/LiFePO4 (LFP), Li/LiNi0.5Co0.2Mn0.3O2 (NCM523) and Li-S full batteries. The reaction mechanism is confirmed by density functional theory calculations, various electrochemical characterizations, and applying designed azo compounds. This new and universal strategy may pave a way to resolve the bottle-neck interfacial issues of lithium metal batteries by organic compounds