| AVS 60th International Symposium and Exhibition | |
| Thin Film | Monday Sessions |
| Session TF+EN-MoM |
| Session: | ALD for Energy |
| Presenter: | C. Liu, University of Maryland, College Park |
| Authors: | C. Liu, University of Maryland, College Park X. Chen, University of Maryland, College Park M. Schroeder, University of Maryland, College Park K. Gregorczyk, University of Maryland, College Park S.B. Lee, University of Maryland, College Park and Korea Advanced Institute of Science and Technology G.W. Rubloff, University of Maryland, College Park |
| Correspondent: | Click to Email |
Nanowire arrays improve ion access and transport to utilize electrode materials, but the potential power-energy advantage of nanostructuring also requires fast electron transport to the ion storage material throughout high-aspect ratio nanowire geometries. To realize this for high performance nanostructured energy storage, we fabricated uniformly aligned arrays of core-shell nanotube devices (half-cells) by atomic laser deposition (ALD) into anodic aluminum oxide (AAO) templates, using ruthenium (Ru) metal as current collecting layer and then crystalline V2O5 as active battery material to form composite nanoelectrodes penetrating part way into the AAO nanopores. The extraordinary conformality of ALD enables controlled formation of the coaxial electrode, with highly conductive Ru metal providing fast electron transport to overlying V2O5 storage material.
The 3-D V2O5-Ru coaxial nanocathode array was configured as a half-cell, with LiPF6 based organic electrolyte in the nanopores and a separator and Li anode incorporated into a coin cell. A high specific capacity of 172 mAh/g was measured at 1C rate over the voltage range 4.0-2.6 V corresponding to 1 Li per V2O5. The areal capacity of 59 uAh/cm2 was 46X that of a planar V2O5 thin film cathode. Excellent cycling performance was demonstrated by capacity retention of 79% after 1000 cycles. Energy density was maintained well at high power – 129mAh/g at 50C rate and 82mAh/g at 200C rate, corresponding to 21 and 52 kW/kg power respectively. Cyclic voltammetry indicates that the capacity at high rate is dominated by double-layer capacitance rather than intercalation processes. The crucial role of electron transport was illustrated by the 4X reduction in capacity - even at 1C rate - when the 15um deep Ru current collector was replaced by a 0.6um TiN. Part of this difference may be the absence of the TiN current collector adjacent to most of the V2O5 storage layer.