| AVS 61st International Symposium & Exhibition | |
| Thin Film | Tuesday Sessions |
| Session TF+EN+PS-TuA |
| Session: | ALD for Energy |
| Presenter: | Chanyuan Liu, University of Maryland, College Park |
| Authors: | C. Liu, University of Maryland, College Park X. Chen, University of Maryland, College Park E. Gillette, University of Maryland, College Park A.J. Pearse, University of Maryland, College Park A.C. Kozen, University of Maryland, College Park M.A. Schroeder, University of Maryland, College Park K. Gregorczyk, University of Maryland, College Park S.B. Lee, University of Maryland, College Park G.W. Rubloff, University of Maryland, College Park |
| Correspondent: | Click to Email |
A self-aligned nanostructured battery fully confined within a single nanopore presents a powerful platform to determine the performance and cyclability limits of nanostructured storage devices. We have created and evaluated such structures, comprised of nanotubular electrodes and electrolyte confined within anodic aluminium oxide (AAO) nanopores as “all-in-one” nanopore batteries. The nanoelectrodes include metal (Ru or Pt) nanotube current collectors with crystalline V2O5 storage material on top of them, penetrating part way into the AAO nanopores to form a symmetric full storage cell, with anode and cathode separated by an electrolyte region.
The unprecedented thickness and conformality control of atomic layer deposition (ALD) and the highly self-aligned nanoporous structure of anodic aluminum oxide (AAO) are essential to enable fabrication of precision, self-aligned, regular nanopore batteries, which display exceptional power-energy performance and cyclability when tested as massively parallel devices (~2billion/cm2), each with ~1μm3 volume (~1fL).
To realize these “all-in-one” nanopore batteries, we focused on the precise control of Ru and Pt thin film conformality inside very high aspect ratio (300:1) AAO nanopores by thermal ALD process. 7.5nm thick Ru and Pt are optimized to be 15µm deep at both sides of 50µm long AAO pores in order to provide fast electron transport to overlying V2O5 at both anode and cathode sides, while keeping them spatially and electrically isolated. Active storage layers of 23nm thick crystalline V2O5 were deposited inside the metal nanotubes to form core-shell nanotubular structures at low temperature (170°C) using O3 as the oxidant, with <001> direction perpendicular to tube surface and RMS roughness ~4nm. Then the V2O5 was prelithiated at one end to serve as anode while pristine V2O5 without Li at the other end served as cathode, enabling the battery to be cycled between 0.2V and 1.8V and to achieve full theoretical Faradaic capacity of the V2O5. Capacity retention of this full cell at high power (relative to 1C rates) is 95% at 5C and 46% at 150C rates (i.e., 24 sec charge/discharge time). At 5C rate (12 min charge-discharge cycle), 81.3% capacity remains after 1000 cycles. These performance metrics are exceptional, exceeding those of most prototypes reported in the literature. These results demonstrate the promise of ultrasmall, self-aligned/regular, densely packed nanobattery structures as a building block for high performance energy storage systems.