Abstract
Construction of metal oxide nanoparticles as anodes is of special interest for next-generation lithium-ion batteries. The main challenge lies in their rapid capacity fading caused by the structural degradation and instability of solid-electrolyte interphase (SEI) layer during charge/discharge process. Herein, we address these problems by constructing a novel-structured SnO2-based anode. The novel structure consists of mesoporous clusters of SnO2 quantum dots (SnO2 QDs), which are wrapped with reduced graphene oxide (RGO) sheets. The mesopores inside the clusters provide enough room for the expansion and contraction of SnO2 QDs during charge/discharge process while the integral structure of the clusters can be maintained. The wrapping RGO sheets act as electrolyte barrier and conductive reinforcement. When used as an anode, the resultant composite (MQDC-SnO2/RGO) shows an extremely high reversible capacity of 924 mAh g−1 after 200 cycles at 100 mA g−1, superior capacity retention (96%), and outstanding rate performance (505 mAh g−1 after 1000 cycles at 1000 mA g−1). Importantly, the materials can be easily scaled up under mild conditions. Our findings pave a new way for the development of metal oxide towards enhanced lithium storage performance.
Highlights
IntroductionWe develop an easy and cheap route of fabricating a novel and hierarchical structure of SnO2-based anode, in which SnO2 QD clusters with internal mesopores are wrapped dexterously with reduced graphene oxide sheets (denoted as MQDC-SnO2/RGO)
The superiority of this novel structure lies in the multiple virtues: (1) the ultra-small size (~3 nm) of the SnO2 QDs and the mesopores assembled in clusters of micrometer size would shorten the diffusion length of Li+ and provide extensive surface for lithiation/delithiation reaction; (2) the amorphous carbon matrix around the SnO2 QDs and the RGO shell outside the clusters greatly reinforce the electronic conductivity of the composite; (3) the SnO2 QDs are intactly encapsuled in the dual carbon coating layers, which restrain the formation of solid–electrolyte interphase (SEI)
SnO2 QDs were prepared in aqueous environment at room temperature, resulting in nanoparticles of ~3 nm as observed by TEM and HRTEM (Supplementary Fig. S2), close to the computed value from the X-ray diffraction (XRD) (Supplementary Fig. S3, Table S1)
Summary
We develop an easy and cheap route of fabricating a novel and hierarchical structure of SnO2-based anode, in which SnO2 QD clusters with internal mesopores are wrapped dexterously with reduced graphene oxide sheets (denoted as MQDC-SnO2/RGO) The superiority of this novel structure lies in the multiple virtues: (1) the ultra-small size (~3 nm) of the SnO2 QDs and the mesopores assembled in clusters of micrometer size would shorten the diffusion length of Li+ and provide extensive surface for lithiation/delithiation reaction; (2) the amorphous carbon matrix around the SnO2 QDs and the RGO shell outside the clusters greatly reinforce the electronic conductivity of the composite; (3) the SnO2 QDs are intactly encapsuled in the dual carbon coating layers (amorphous carbon and RGO), which restrain the formation of SEI. When used as anode material, the resultant MQDC-SnO2/RGO shows superior performances
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