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).
Materials for lithium‐ion batteries (LIBs) with excellent electrochemical performance are of significance to meet the increasing demand for rechargeable batteries. Niobium pentoxide (Nb2O5), as an intercalation material with promising electrochemical properties has caught our attention. In this study, Nb2O5 nanoparticles were successfully synthesized through a classical sol‐gel process. The nanoparticles with a size of less than 5 nm were uniformly coated on carbon materials, i. e., reduced graphene oxide (rGO) and three‐dimensionally ordered macroporous (3DOM) carbon, under the same proportion, to explore which kind of carbon materials is more suitable to improve the electrochemical performance of Nb2O5 as an anode for LIBs. Nb2O5/3DOM carbon composite exhibited a superior electrochemical performance to the other two materials, where a high reversible capacity of 519 mA h g−1 could be maintained at the current density of 5.0C (C=201.7 mA g−1). Furthermore, the specific capacity of Nb2O5/3DOM carbon composite maintained 1163 mA h g−1 at the current density of 0.2C (C=201.7 mA g−1) after 100 cycles.
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