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 activation 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 applications of flexible and wearable batteries.