Micro Energy Storage & Smart Power

In the Micro Energy Systems Group at Fraunhofer IZM, electrochemists, materials scientists and physicists work together with electronics engineers on an interdisciplinary basis to provide adapted power supplies for the microsystems developed at the institute and to exploit the diverse technological possibilities in the area of silicon-wafer-level integration at IZM in order to develop miniaturized batteries and converters. The development focus is on integrated micro-batteries and the smallest solar modules for energy-autonomous sensors and data loggers. The developments are supported by numerical simulations. The group is also involved in material development projects for new battery systems such as Li-metal batteries and solid-state batteries.

The smallest micro-batteries (rechargeable and primary) with customer specific requirements can be developed and manufactured as prototypes in quantities up to approximately 10,000 pieces.

Another focus of the group is the development of zinc-based energy storage devices, which can generate both hydrogen and electricity on demand and are highly relevant to the energy transition.

The group also provides testing and consultancy services for all types of electrochemical storage. Laboratories are available for the production and characterisation of battery electrodes and electrolytes, as well as a prototype line for the prototype fabrication of micro-batteries. More than 30 patents have been filed in the field of micro energy systems.

Electrochemical micro-storage and harvesting

Energy autarkic microsystems and intelligent, self-sufficient sensor nodes will lead to completely new applications in the future. The power supply required for this must be an integral part of the early stages of development and requires the cooperation of developers, manufacturers and end users.

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Micro Batteries

Customised micro-batteries

Where ever ultra-miniaturization is required like wireless sensor nodes or medical applications, the silicon embedded secondary lithium ion battery developed at Fraunhofer IZM can be used as electrical buffer storage. Shape and size as well as voltage, capacity and power performance can be adapted to the application requirements.

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Micro-battery for medical applications

As part of an industrial collaboration, the smallest primary batteries have been developed with a width of only 0.5 mm and a thickness of 0.25 mm. Biocompatibility has been achieved by using a suitable electrolyte, a hermetic seal using low temperature solder and a titanium coating. Electrochemical stability has been optimised for a lifetime of 4 years.

Der Vergleich mit dem 1-Cent-Stück zeigt, wie klein eine 8 mm lange, 0,5 mm breite und 0,25 mm hohe Mikrobatterie ist. Ihre Kapazität sind dennoch 40 µAh
© Fraunhofer IZM

Sens4Bee

Sens4Bee - A range of RFID-based sensors in hives and on individual bees can be used to collect data and analyse bee welfare.

An ultra-small lithium battery and a silicon solar module are being developed. These are integrated by Micro-Sensys GmbH with the smallest sensor transponders and sensor data loggers with an RFID interface in a module so small and light that the bees can carry it on their backs.

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Biene mit Solar-Batterie-Mikromodul
© Fraunhofer IZM
Bee with solar-battery module

Hydrogen Storage

Zn-H2

Based on the development of micro fuel cells for energy self-sufficient sensors, galvanic hydrogen storage systems based on zinc anodes have been developed. This system is being further developed as a rechargeable system in the BMBF project Zn-H2 and is now a very interesting candidate as a low-cost energy storage system in the context of the energy transition. The core of the development is dendrite-free zinc deposition with electronic monitoring and cycle-stable, noble metal-free bi-stable catalysts that alternate between hydrogen and oxygen evolution (HER/OER) in each cycle.

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Aging of lihtium-ion batteries

As part of an EU project (PROMPT), an ageing and state-of-health model for lithium-ion batteries was developed. In addition to the typical variables such as number of cycles, depth of discharge and temperature, the influence of the charging current (fast charging) was investigated.

MATFLEXEND

Fraunhofer IZM is coordinating the FP7 project MATFLEXEND, which is developing new flexible micro-batteries and harvesters that are particularly suitable for integration into portable electronics and smart cards. Development focuses on the use of nanomaterials and printable electrolytes.

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Micro Battery Line

When developing micro batteries, the greatest challenge is to produce hermetically sealed casings. Even tiniest traces of humidity entering the battery would be enough to reduce battery lifetime significantly. The reactive nature of the lithium needs the entire assembly process to happen in high-purity argon gas containment units. The highly complex technology needed is only financially viable if it can produce entire batches of batteries simultaneously on a shared substrate layer or on a silicon wafer.

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Micro Battery Line at the Fraunhofer IZM
© Fraunhofer IZM
 

Flexible batteries for tomorrow’s applications

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Attainable energy density of micro-batteries

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