2D Graphene/MnO Heterostructure with Strongly Stable Interface Enabling High-Performance Flexible Solid-state Lithium-Ion Capacitors

The delicate structural engineering is widely acknowledged as a powerful tool for boosting the electrochemical performance of conversion-type anode materials for lithium storage. Here, a general electrostatic self-assembly strategy is proposed for the in situ synthesis of MnO nano-cabbages on negatively charged reduced graphene oxide (rGO/MnO). The strong interfacial heterostructure and robust lithium storage mechanism related to fast Li+ diffusion kinetics and high Li-adsorption ability of rGO/MnO heterostructure are confirmed through operando experimental characterizations and theoretical calculation. Owing to the rapid charge transfer, enriched reaction sites, and stable heterostructure, the as-synthesized rGO/MnO anode delivers a high capacity (860 mAh g(-1) at 0.1 A g(-1)), superior rate capability (211 mAh g(-1) at 10 A g(-1)), and cycle stability. Notably, the as-assembled flexible pouch cell of activated carbon//rGO/MnO solid-state lithium-ion capacitors (LICs) possesses an exceptional energy density of 194 Wh kg(-1) and power density of 40.7 kW kg(-1), both of which are among the highest flexible solid-state LICs reported so far. Further, the LICs possess an ultralong life span with approximate to 77.8% retention after 10 000 cycles and extraordinary safety, demonstrative of great potential for practical applications.