Dispersed Mn2Co2C nanoparticles in interconnected nitrogen-doped carbon framework as cathode catalysts for efficient and long-life Li-CO2 batteries

The Li-CO2 batteries are concerned as a potential energy conversion and storage system which can not only effectively capture CO2 gas but also offer a high energy density. Therefore, they can be widely used in CO2- enriched environments such as submarine operations. However, the development of Li-CO2 batteries is still restricted by the high polarization and poor cycle performance mainly due to the insulating discharge product, e. g., Li2CO3. Herein, the Mn2Co2C nanoparticles dispersed in interconnected nitrogen-doped carbon frameworks (Mn2Co2C@NC), obtained by pyrolyzing MnCo Prussian blue analogous (MnCo-PBA), are first utilized as the cathode materials in Li-CO2 batteries. The batteries deliver a high discharge capacity (18962 mAh g(-1) at 100 mA g(-1)), the lowest overpotential (1.47 V), and the best cycle performance (330 cycles, close to 1800 h, with a limited capacity of 500 mAh g(-1) at 200 mA g(-1)). The good cycling stability under 200 mA g(-1) is more prominent for current Li-CO2 batteries. The superior performance of Mn2Co2C@NC is ascribed to abundant catalytic sites of Mn/Co-nitrogen-carbon (Mn/Co-NC) and nitrogen-doped carbon, which have outstanding adsorption and acti-vation effects on CO2. Meantime, the robust interconnected carbon framework provides fast electron/electrolyte transport paths and a large deposition space of Li2CO3. The density functional theory calculations reveal the strong adsorption of Li+ and CO2, strong catalytic performance for CO2 reduction, and excellent electrical conductivity of the Mn/Co-NC and nitrogen-doped carbon active sites. Finally, when combining a gel electrolyte, to the best of our knowledge, for the first time the fabricated quasi-solid-state Li-CO2 batteries demonstrate good cycling stability with high deliverable specific discharge capacity, highlighting its great potential for the ap-plications of flexible and wearable batteries.