SnO₂ Anode Surface Passivation by Atomic Layer Deposited HfO₂ Improves Li-Ion Battery Performance

For the first time, it is demonstrated that nanoscale HfO₂ surface passivation layers formed by atomic layer deposition (ALD) significantly improve the performance of Li ion batteries with SnO₂-based anodes. Specifically, the measured battery capacity at a current density of 150 mAg^-1 after 100 cycles is 548 and 853 mAhg^-1 for the uncoated and HfO₂-coated anodes, respectively. Material analysis reveals that the HfO2 layers are amorphous in nature and conformably coat the SnO₂-based anodes. In addition, the analysis reveals that ALD HfO₂ not only protects the SnO2-based anodes from irreversible reactions with the electrolyte and buffers its volume change, but also chemically interacts with the SnO₂ anodes to increase battery capacity, despite the fact that HfO₂ is itself electrochemically inactive. The amorphous nature of HfO₂ is an important factor in explaining its behavior, as it still allows sufficient Li diffusion for an efficient anode lithiation/delithiation process to occur, leading to higher battery capacity.