Abstract
The best electrode performance of metal oxide–graphene nanocomposite material for lithium secondary batteries can be achieved by using the colloidal mixture of layered CoO2 and graphene nanosheets as a precursor. The intervention of layered CoO2 nanosheets in-between graphene nanosheets is fairly effective in optimizing the pore and composite structures of the Co3O4–graphene nanocomposite and also in enhancing its electrochemical activity via the depression of interaction between graphene nanosheets. The resulting CoO2 nanosheet-incorporated nanocomposites show much greater discharge capacity of ~1750 mAhg−1 with better cyclability and rate characteristics than does CoO2-free Co3O4–graphene nanocomposite (~1100 mAhg−1). The huge discharge capacity of the present nanocomposite is the largest one among the reported data of cobalt oxide–graphene nanocomposite. Such a remarkable enhancement of electrode performance upon the addition of inorganic nanosheet is also observed for Mn3O4–graphene nanocomposite. The improvement of electrode performance upon the incorporation of inorganic nanosheet is attributable to an improved Li+ ion diffusion, an enhanced mixing between metal oxide and graphene, and the prevention of electrode agglomeration. The present experimental findings underscore an efficient and universal role of the colloidal mixture of graphene and redoxable metal oxide nanosheets as a precursor for improving the electrode functionality of graphene-based nanocomposites.
Highlights
The best electrode performance of metal oxide–graphene nanocomposite material for lithium secondary batteries can be achieved by using the colloidal mixture of layered CoO2 and graphene nanosheets as a precursor
Most of the exfoliated CoO2 nanosheets possess the lateral size of several hundreds of nanometers, which is comparable with the reported lateral dimension of graphene oxide (G-O) nanosheet[28]
We are successful in developing a very efficient method to improve the electrode performance of graphene-based nanocomposite materials using the colloidal mixture of layered metal oxide and graphene nanosheet as a precursor
Summary
The best electrode performance of metal oxide–graphene nanocomposite material for lithium secondary batteries can be achieved by using the colloidal mixture of layered CoO2 and graphene nanosheets as a precursor. The intervention of layered CoO2 nanosheets in-between graphene nanosheets is fairly effective in optimizing the pore and composite structures of the Co3O4–graphene nanocomposite and in enhancing its electrochemical activity via the depression of interaction between graphene nanosheets. Among diverse metal oxide nanosheets, redoxable transition metal oxide nanosheets such as CoO2, [Mn1/3Co1/3Ni1/3]O2, and MnO2 show sufficiently high electrical conductivity and high electrochemical activity[25,26,27] Such redoxable metal oxide nanosheets can be suitable additives for optimizing the composite structure, pore structure, and performance of graphene-based nanocomposite electrode materials. At the time of publication of this study, we are aware of no report about the use of the mixed colloidal suspension of layered metal oxide and graphene nanosheets as a precursor for the optimization of the electrode performance of graphene-based nanocomposites for secondary batteries. The present strategy is extended by the incorporation of layered MnO2 nanosheets into the Mn3O4–graphene nanocomposite
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