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The two major limitations in the application of SnO2 for lithium-ion battery (LIB) anodes are the large volume variations of SnO2 during repeated lithiation/delithiation processes and a large irreversible capacity loss during the first cycle,which can lead to a rapid capacity fade and unsatisfactory initial Coulombic efficiency (ICE).To overcome these limitations,we developed composites of ultrafine SnO2 nanoparticles and in situ formed Co(CoSn) nanocrystals embedded in an N-doped carbon matrix using a Co-based metal-organic framework (ZIF-67).The formed Co additives and structural advantages of the carbon-confined SnO2/Co nanocomposite effectively inhibited Sn coarsening in the lithiated SnO2 and mitigated its structural degradation while facilitating fast electronic transport and facile ionic diffusion.As a result,the electrodes demonstrated high ICE (82.2%),outstanding rate capability (~ 800 mAh g-1 at a high current density of 5 A g-1),and long-term cycling stability (~ 760 mAh g-1 after 400 cycles at a current density of 0.5 A g-1).This study will be helpful in developing high-performance Si (Sn)-based oxide,Sn/Sb-based sulfide,or selenide electrodes for LIBs.In addition,some metal organic frameworks similar to ZIF-67 can also be used as composite templates.