The Nanostructure Modulation Of SnO₂/C Composites And Their Energy Storage Properties

Recently,high-performance lithium-ion batteries(LIBs)have been widely investigated for promoting the development of electric vehicles(EVs)and hybrid electric vehicles(HEVs)worldwide.At present,the traditional commercial graphite anodes have a limited theoretical capacity of 372 mAh g-1.So people desire to develope some alternative anode materials to replace graphite.SnO2 is a promising anode material for lithium-ion batteries because of its low cost and high theoretical specific capacity(1494 mAh g-1),but its practical application is greatly limited by undesirable rapid capacity fading,low initial coulombic efficiency and poor rate performance.The problems can be ascribed to the large volume variation(-300%)during the long term charge-discharge process,the irreversible reaction in the first cycle,and the low electronic conductivity of SnO2.These problems can be improved by enhancing conductivity,introducing amorphous phase and building nanoarchitectures,which homogenizes the redox reactions and stabilizes fine,fracture-resistant Sn precipitates in the Li2O matrix.In this paper,firstly pure SnO2 and carbon coated SnO2(SnO2/C)nanosheet arrays were prepared,then porous carbon coated SnO2-?/C(porous SnO2-?/C)nanosheet arrays and porous SnO2 were prepared by HCl etching SnO2/C nanosheet,and the four samples were used for anode material for lithium ion batteries.SnO2-?/C nanosheet arrays had the porous structure with carbon shell for the composite materials,crystalline and amorphous domains coexist in the SnO2-? phase,which was beneficial for improved structural stability and enhanced Li+diffusion.The results showed that the as-prepared porous SnO2-?/C nanosheet arrays electrode delivered a reversible charge specific capacity of 1378.6 mAh g-1 at the current density of 0.1 A g-1,even at high current density of 2 A g-1,it still delivered a specific capacity of 574.4 mAh g-1,It had a 80.5%capacity retention after 1000 cycles at 1 A g-1.While the SnO2 nanosheet arrays electrode had a lower reversible charge specific capacity of 1067.3 mAh g-1 at 0.1 A g-1,at high current density of 2 A g-1,it just delivered a low specific capacity of 51.59 mAh g-1.It only had 10.1%capacity retention after 100 cycles.The porous SnO2-?/C nanosheet arrays showed much increased specific capacity,high rate capability and cycling stability than SnO2,porous SnO2,and SnO2/C nanosheet arrays,demonstrating that the porous structure of SnO2-?/C nanosheets are essential for better lithium-ion storage performance.What's more,we fabricated a full cell consisting of porous SnO2-?/C nanosheet arrays anode and LiMn2O4 nanowall arrays cathode,which gived a capacity retention of 77.3%over 1000 cycles at 1 A g-1,demonstrating the promising practical application of porous SnO2-?/C nanosheet arrays in real lithium ion battery.This work provided a smart electrode design that could be applicable for other transition metal oxide-based anodes for high performance lithium-ion batteries.