Realizing uniform dispersion of MnO2 with the post-synthetic modification of metal-organic frameworks (MOFs) for advanced lithium ion battery anodes

MnO2 nanoparticles were uniformly loaded on the surface of zeolitic imidazolate frameworks (ZIF-67 and ZIF-8) with ligand modification via a facile method with no other impurities introduced, with an average diameter of less than 10 nm. The MnO2/ZIF-COOH composites with stable structures can effectively alleviate expansion tension and provide a fast ion transport channel during electrochemical performance tests. The introduction of carboxyl (-COOH) increases the specific capacity due to Li insertion, enhances the conductivity with ionization, and improves stability through the formation of H-bonds. When used as an anode for lithium ion batteries, the MnO2/ZIF-67-COOH composite exhibits an excellent rate performance (1208 mA h g(-1) at 50 mA g(-1), 931 mA h g(-1) at 100 mA g(-1), 828 mA h g(-1) at 200 mA g(-1), 684 mA h g(-1) at 500 mA g(-1), 566 mA h g(-1) at 1000 mA g(-1), 431 mA h g(-1) at 2000 mA g(-1), and 242 mA h g(-1) at 5000 mA g(-1)) and high cycle stability even at high rates (a high capacity of 664 mA h g(-1) is achieved at 1000 mA g(-1) and is maintained at approximately 100% after 100 cycles).