SnO 2 Anode Surface Passivation by Atomic Layer Deposited HfO 2 Improves Li‐Ion Battery Performance

For the first time, it is demonstrated that nanoscale HfO 2 surface passivation layers formed by atomic layer deposition (ALD) significantly improve the performance of Li ion batteries with SnO 2 ‐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 HfO 2 ‐coated anodes, respectively. Material analysis reveals that the HfO 2 layers are amorphous in nature and conformably coat the SnO 2 ‐based anodes. In addition, the analysis reveals that ALD HfO 2 not only protects the SnO 2 ‐based anodes from irreversible reactions with the electrolyte and buffers its volume change, but also chemically interacts with the SnO 2 anodes to increase battery capacity, despite the fact that HfO 2 is itself electrochemically inactive. The amorphous nature of HfO 2 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.