Precise growth of Al2O3/SnO2/CNTs composites by a two-step atomic layer deposition and their application as an improved anode for lithium ion batteries

SnO2 is considered as a high capacity anode material for lithium ion batteries. However, the poor cycling stability has seriously hindered its practical applications. In this work, we designed and prepared Al2O3/SnO2/CNTs composites by uniformly and conformally depositing SnO2 and Al2O3 on carbon nanotubes (CNTs) via a simple two-step atomic layer deposition (ALD) process. The thicknesses of SnO2 and Al2O3 were precisely controlled by tuning the number of ALD-cycle to optimize the cycling performance of Al2O3/SnO2/CNTs electrodes. The ultrathin SnO2 layer with a thickness of approximate 2.8 nm on CNTs exhibits a high capacity and an enhanced cycling stability due to the buffering effect of CNTs and limited SnO2 crystallization after the first step deposition. On this basis, Al2O3/SnO2/CNTs electrodes exhibit a significantly improved cycling stability, rate capability and Coulombic efficiency due to surface stability and the structural integrity brought by Al2O3 passivation after the second step deposition. Especially, 10-Al2O3/SnO2/CNTs electrode deliveries a discharge capacity of 581.6 mAh g(-1) at a current density of 100 mA g(-1) and capacity retention is 90.85% against 2nd cycle after 200 charge-discharge cycles. We believe that this work provides an effective way for the design of high performance anode materials in advanced batteries. (C) 2019 Elsevier Ltd. All rights reserved.