Power and Energy storage at the microscale for autonomous nanostructured wireless sensors – MECANANO

Each 3D device will be fabricated and compared with a planar one to demonstrate the potential of the 3D technology. The main issue of the MECANANO project is to achieve at IEMN and IMN the step conformal deposition of the electrode materials and the electrolyte on the high density 3D silicon scafold. A collective fabrication of 2 devices will be developed.

To get autonomous smart microsystem, a miniaturized power source should be integrated. As the device is surface limited, the energy and power performances of commercially available planar microbatteries and micro-supercapacitors are not sufficient to reach this goal. To improve their performances while keeping constant the footprint area of such devices, a 3D topology is proposed. The silicon micropillars and microtubes fabricated by a top down approach allows to reach a high area enlargement factor (AEF). Energy density can be increased by one or two orders of magnitude compared to standard planar micro-devices, thus providing improved autonomy to the powered microsytems.
Step conformal deposition of platinum (current collector) and TiO2 (negative electrode of the Li-ion microbattery) are performed on the 3D structures by Atomic Layer Deposition facility. With a 3D scaffold having an AEF close to 25 combined with a 150 nm thick TiO2, a surface capacity of 0.2 mAh/cm2 at C/10 is reported.
A micro-supercapacitor electrode based on a thin manganese dioxide film is conformably grown by pulsed electrodeposition on the 3D topologies. A MnO2 film (275 nm thick) reaches 250 mF/cm² at 5 mV/s. The surface capacitance is drastically enhanced compared to a standard 2D electrode with a comparable thickness.

An new ALD equipment has been installed recently at IEMN to develop the lithiated compound for 3D conformal deposition.

An all solid state 3D microsupercapacitor based on transition metal oxide is under fabrication in the framework on the project

Silicon-microtube scaffold decorated with anatase TiO2 as a negative electrode for a 3D litium-ion microbattery
EUSTACHE E., TILMANT P., MORGENROTH L., ROUSSEL P., PATRIARCHE P., TROADEC D., ROLLAND N., BROUSSE T., LETHIEN C.
Adv. Energy Mater., (2014) 1301612,

High surface capacity Li-ion all solid state 3D microbattery based on anatase TiO2 deposited by ALD on silicon microstructures
EUSTACHE E., TILMANT P., MORGENROTH L., ROUSSEL P., ROLLAND N., BROUSSE T., LETHIEN C.
224th ECS Meeting, Symposium E2 - Atomic Layer Deposition Applications 9, San Francisco, CA, USA, october 27-november 1, 2013
ECS Trans., 58, 10 (2013) 119-129, related to meeting abstract MA2013-02(24):1875 (published october 2013)

High areal capacitance micro-supercapacitor based on electrodeposited MnO2 thin films on silicon 3D microstructures
EUSTACHE E., TILMANT P., MORGENROTH L., ZEGAOUI M., DOUARD C., LETHIEN C., BROUSSE T.
224th ECS Meeting, Symposium B5 - Electrochemical Capacitors : Fundamentals to Applications, San Francisco, CA, USA, october 27-november 1, 2013, Abstract B5-0619

The MECANANO project aims to produce a micropower source for wireless sensor nodes. In order to supply energy as well as power depending on the proposed applications, the MECANANO project will focus to the technological fabrication of 4 microstorage devices with enhanced performances by a 3D structure leading to a large deployement of specific area. In the first phase of the project, the 4 devices will be developped individually. In the second phase, a collective integration is proposed. All the fabricated devices will use the same generic platform based on the micro/nanomachining of a silicon wafer. The proposed fabrication process will be compatible with the classical ons developed in the microelectronic industry.

To reach the proposed objectives, the MECANANO project is based on 2 complementaries laboratories:
- l’IEMN, CNRS UMR 8520
- l’IMN JR (Institut des Matériaux Jean Rouxel, UMR CNRS 6502)

The main results are the following:
- Fabrication of the generic platform based on the micro/nanomachining of a silicon wafer
- Fabrication of a 3D Li-ion solid state microbattery (5 to 50 mWh/cm2 – 3V – 1000 to 10 000 cycles)
- Technolgical fabrication of 3D microsupercapacitor (30 to 240 µWh/cm2 – 1.5V – 100 000 cycles)
- Fabrication of a 3D electrolytic capacitor (1mF/cm2, 4µWh/cm2 – 5V – 100000 cycles, rise time ~ 10-100ms)
- Fabrication of a 3D electostatic capacitor (1,4 µWh/cm2 ,100µF/cm2 – 10V – 1 000 000 cycles – rise time ~ ms)
- Collective integration of at least 2 complementary devices.