Recent Advances in Three Dimensional Thin Film Microbatteries
- PDF / 658,273 Bytes
- 6 Pages / 595 x 842 pts (A4) Page_size
- 63 Downloads / 200 Views
K10.10.1
Recent Advances in Three Dimensional Thin Film Microbatteries 2
1
2
M. Nathan1*, D. Golodnitsky2,3, V. Yufit1, E. Strauss , T. Ripenbein , I. Shechtman , S. 2 Menkin and E. Peled2 1- Department of Physical Electronics, School of Electrical Engineering; 2- School of Chemistry; 3- Wolfson Applied Materials Research Center, Tel Aviv University, Tel Aviv, 69978, Israel ABSTRACT Autonomous MEMS require similarly miniaturized power sources. We present the first three-dimensional (3D) working thin-film microbattery (MB) technology that is compatible with MEMS requirements. Our 3D MBs are formed in perforated substrates (silicon chip or glass microchannel plate), in which a sandwich-like thin-film battery structure is deposited conformally and sequentially on all available surfaces, using wet chemistry. The area of high aspect ratio holes in the substrate enhances the capacity and energy density per given substrate footprint by more than an order of magnitude. Full 3D cells were manufactured on both glass and silicon substrates. A 3D cell on a micro-channel plate substrate exhibited a capacity of ca. 2mAh/cm2, in good agreement with the ca. 23 times area gain provided vs an identical footprint 2D cell.
INTRODUCTION The need for miniaturized power sources for MEMS has been recognized for some time [1] and various efforts are underway to provide MBs [2] and other devices such as combined batteries/solar cells[3]. However, to date, none of these efforts has produced a working prototype that can supply the required energy and capacity [4]. In their recent review of the subject, Long et al. list proposed 3D architectures and technologies, but acknowledge that operational, fully 3D batteries have not yet been achieved. In this paper we present results of our effort to develop a working, truly 3D thin-film MB technology, which can provide the required capacity and geometrical energy density for autonomous MEMS. A more detailed paper is to be published separately [5]. Our 3D thin-film MBs resemble in their layered structure planar (2D) thin-film batteries, e.g. the Li and Li-ion batteries developed at Oak Ridge National Laboratories by a group led by Bates [6]. The capacity of 2D batteries is limited by the active cathode volume, given by the substrate area multiplied by cathode thickness. According to Long et al [4], the best 2D Li thin-film batteries have an energy density of ~ 2 J mm-3 or 0.56 mWh mm-3. For a 5µm thick cathode on a substrate "footprint" of 1 cm2, this translates into a "geometrical" energy density of 0.28 mWh/cm2. The best commercial thin-film batteries also have an experimentally measured capacity of 0.133 mAh/cm2 [7], which is quite small. In order to fit projected autonomous MEMS requirements, 2D batteries must be formed on areas larger than a few cm2, areas which will be unavailable in many of these systems. The solution is to move to 3D configurations in which the reduction of the footprint area is compensated by an increase in area in the third (height) dimension. This allows thin-film batter
Data Loading...
