Designing of carbon cloth @ Co-MOF @ SiO2 as superior flexible anode for lithium-ion battery

Abstract

Silica combining high theoretical specific capacity (1965 mAh g−1), abundant storage, light weight, small size, and no harmful substances has been recognized as an alternative anode material for lithium-ion batteries. However, low diffusivity of lithium ions, poor natural electrical conductivity and disappointing structural stability of silica represents a key problem that severely limits their practical applications. Herein, we report on designing a composite structure of CC @ Co-MOF @ SiO2, in which 3D porous and carbonized structure of cobalt-metal organic framework (Co-MOF) can adapt to the huge volume change of SiO2, inhibit the aggregation of SiO2 nanospheres and buffer mechanical stress. Meanwhile, SiO2 nanospheres with a smaller diameter not only restrain their own volume expansion but also enable more SiO2 nanospheres to occupy or attach to the void of the Co-MOF, resulting in an increase of the amount of active material in the electrode which can greatly boost the specific capacity of batteries. Carbon cloth (CC) as the substrate can effectively improve conductivity of CC @ Co-MOF @ SiO2 as well as stability of the structure and interface can be maintained to a certain extent. Profiting from the synergistic effect of the components, the CC @ Co-MOF @ SiO2 composite presents outstanding electrochemistry properties as electrode materials for lithium-ion batteries. The first discharge capacity of CC @ Co-MOF @ SiO2 is 1799.4 mAh g−1 at the current density of 1 A g−1. CC @ Co-MOF @ SiO2 composite material exhibits an outstanding reversible capacity of 1565 mAh g−1 at the current density of 1 A g−1 after 300 cycles and the capacity retention rate is even as high as 86.97%. The synergistic effect of the components of the CC @ Co-MOF @ SiO2 composite is also discussed. The present synthesis method can be easily extended to produce other CC @ Co-MOF based oxide composite for lithium-ion batteries or other applications.