Hierarchical porous CoOx/carbon nanocomposite for enhanced lithium storage

Abstract

Transition metal oxides have high theoretical capacities when served as anode for lithium-ion battery but suffer poor cyclability and high rate capacity due to large volumetric changes and low ions diffusion kinetics. To issue these problems, we introduce hierarchical porous structure into CoOx/carbon nanocomposite through constructing SiO2-CoOx-phenolic-resin gel coupled with subsequent high temperature annealing and removing SiO2 template. In this nanocomposite, Co3O4 and Co nanoparticles with the size of about 10nm uniformly disperse in the hierarchical porous carbon matrix. The hierarchical porous structure can provide multistage transfer channels for lithium-ions, which enhances the lithium-ion diffusion kinetics in CoOx nanoparticles. Meanwhile the hierarchical porous structure can accommodate volumetric changes of CoOx nanoparticles during electrochemical cycling, which assure the electrode integrity. The carbon matrix and metal Co nanoparticles are able to provide rapid transfer channels for electrons. Therefore, the hierarchical porous CoOx/carbon nanocomposite electrode delivers excellent cyclability and high-rate capacities. The reversible capacities remain 381mAh g−1 after 500cycles at 1.0A g−1, and 298mAh g−1 after 1000cycles at 5.0A g−1. The reversible capacity at 20A g−1 remains 195mAh g−1, which is 25.6% of that at 0.2A g−1. The full battery using the hierarchical porous CoOx/C nanocomposite as the negative electrode and lithium nickel cobalt manganese oxide as the positive electrode delivers first energy density of 151mWh g−1 based on the whole mass of negative/positive electrodes. This work provides a possible pathway to achieve promising electrode materials for lithium-ion batteries.