Design and synthesis of a 3-D hierarchical molybdenum dioxide/nickel/carbon structured composite with superior cycling performance for lithium ion batteries†
Molybdenum dioxide is an attractive material for anodes of lithium ion batteries due to its high theoretical capacity, more than twice that of graphite. However, slow electrode reaction kinetics and structural degradation caused by large volume changes and phase separation during cycling hinder its practical application. To solve these problems, we design and fabricate a novel, 3-D hierarchical MoO2/Ni/C architecture by a combination of a hydrothermal method with chemical vapor deposition. The nickel nanoparticles are in situ formed and disperse uniformly with flower-like MoO2 particles, which are coated by thin carbon layers. The Ni particles act as a catalyst during the carbon coating process to promote the in situ growth of graphene in the carbon layer. Together, MoO2 and nickel nanoparticles, as well as amorphous carbon and graphene sheets build a 3-D hierarchical robust MoO2/Ni/C structure with a good electronically conductive network and lots of void space. Such a 3-D hierarchical structure combines multiple advantageous features, including an enhanced 3-D electronically conductive network, plenty of tunnels for electrolyte solution penetration, void space for volume change accommodation, and more surface areas for the electrode reaction. The manufactured MoO2/Ni/C composite exhibits a high reversible capacity, and excellent rate capability of 576 and 463 mA h g−1 at current densities of 100 and 1000 mA g−1, respectively. The excellent cycling performance is recorded with a capacity of 445 mA h g−1 maintained at 1000 mA g−1 after 800 cycles. The proposed synthesis process is simple and the design concept can be broadly applied, providing a novel, general approach towards manufacturing of metal oxide/metal/carbon (graphene) composites for high energy density storage or other electrochemical uses.