Ultrathin CoOOH/Co(OH)2 hybrid nanosheets for high-performance anodes of lithium-ion batteries

Abstract

CoOOH and Co(OH)2 have great potential in lithium-ion battery anodes due to their high theoretical specific capacities. But they suffer from large volume change during the cycle and hence display fast capacity fading. Carbon coated ultrathin two-dimensional porous nanostructure engineering can be conducive to improving cycling stability of both CoOOH and Co(OH)2, but it is a huge challenge. Herein, a tetraethyl orthosilicate (TEOS) assisted synthesis of carbon coated ultrathin porous CoOOH/Co(OH)2 hybrid nanosheets (COH@C NSs) has been proposed and achieved successfully. This original idea using the TEOS as the reactant not only constructs the ultrathin two-dimensional nanosheets as a structure directing reagent but also forms a porous structure as a precursor of SiO2 pore templates. As a result, the COH@C NSs integrate the advantages of ultrathin two-dimensional nanosheets, porous structure and carbon coating, and hence have significantly improved structural stability and electrochemical kinetics during the cycle, delivering 845.3 mA h g−1 in 350th cycle at 200 mA g−1 and 696.2 mA h g−1 in 400th cycle at 1000 mA g−1. This work gives a unique insight for engineering ultrathin two-dimensional porous nanostructure of high-capacity CoOOH/Co(OH)2 hybrid electrode.