Metal-Organic Framework-Derived Hierarchical MnO/Co with Oxygen Vacancies toward Elevated-Temperature Li-Ion Battery.

Transition metal oxides for high-temperature lithium-ion batteries have captivated orchestrated efforts for next-generation high-energy-density anodes. However, due to inherent low tap density, poor conductivity, and structural instability, their poor cyclability capacity and rate performance at elevated temperatures hinder further implementation. Oxygen vacancies (Ov) engineered by manipulating the active sites and electrical conductivity is a promising method for superior lithium storage. Herein, hierarchical MnO/Co nanoparticle-embedded N-doped carbon nanotube (CNT)-assembled carbonaceous micropolyhedrons (Ov-MnO/Co NCPs) are constructed by a "4S" self-assembly, self-template, self-adaptive, and self-catalytic metal-organic framework template method with in situ oxygen vacancies introduced. Impressively, the internal nanoparticles with metallic Co and the external N-doped carbonaceous matrix entangled by fluffy self-generated CNTs synchronously constructed hierarchical micro/nano-secondary hybrids, facilitating highly compacted density, staggered conductive network, multidirectional diffusion pathways, and accelerated electrochemical kinetics. Experimental and density functional theory investigations systematically manifested that the Ov alongside the local built-in electric field within the crystal lattice induced the boosted electrical conductivity, additional active sites, and alleviated structural expansion, further achieving the exceptional diffusivity coefficient and pseudocapacitive capacity. Benefiting from the integrated structural and compositional optimization, the Ov-MnO/Co NCPs achieved distinguished "3C" performance with superior ultralong cyclability (a volumetric capacity of 1713.5 mAh cm-3 at 1 A g-1 up to 1000 cycles), good rate capacity (a well-maintained capacity of 670.2 mAh g-1 even at 10 A g-1), and considerable high-temperature capability at 60 °C.