Technology Offers Electrical Engineering

Battery electrodes made of silicon layers with optimized porosity and microstructure

The use of silicon as anode material promises high theoretical energy density in lithium-ion batteries. However, the volume of a silicon-based anode may increase substantially during lithiation. In order to solve this problem, scientists at the Institute of Photovoltaics (ipv), University of Stuttgart, now succeeded in developing a method for producing micro-stabilized and porous silicon anodes by means of laser irradiation. The battery electrodes related to this invention offer a high potential for lithiation and at the same time improved mechanical stability. Due to a large active surface they provide high energy density. They can be used for the production of mechanically flexible batteries.



Macro-porous, nanocrystalline silicon layer for lithium-ion batteries

For the production of rechargeable batteries, it is desirable to use silicon as anode material in Li-ion batteries. The use of silicon anodes theoretically increases battery capacity tenfold compared to conventional graphite anodes. However, the attempt had previously failed, since the layers would expand by 300 to 400 % due to the storage of lithium ions in the Si bulk material. This induces a high residual strain and can destroy the bulk Si after only a few charge cycles. In addition, as a consequence of the irreversible reaction between the Si anode and electrolyte a layer of solid electrolyte interphase (SEI) can develop and lead to a low coulombic efficiency. 
Scientists of the University of Stuttgart now succeeded in developing a porous semiconductor layer, which displays a pore distribution from 50 to 3000 nm and eliminates the residual strain. It can be manufactured in a continuous process.



S3L-Inverter: Switching-loss-free 3-level pulse-controlled inverter with snubber circuit

The new Soft Switching Three Level Inverter (S3L – Inverter) is of striking simplicity and is therefore inexpensive. Because of the underlying principle, it works without losses and thus with maximum efficiency. The inverter is easily controlled, has EMC friendly inherent di/dt- and du/dt limitation, and can be built using low-cost standard semiconductors.

Field of use: electric drives, solar power inverter, wind power inverter, uninterruptible power supplies (UPS).





Device for registering the occupancy of tracks in railway traffic

A very common method for determining the occupancy of a rail track is survey via the so-called track circuits. This method involves applying a low voltage to a pair of rail tracks which are isolated from the rest of the network and monitoring whether the voltage is short-circuited by the wheels and axles of a passing train. Rust and dirt that may cover the rail surface over time can create significant problems.

The present invention consists of a device that allows to break through the insulating surface and thus ensures reliable signalling. This is achieved by creating sparks between the carriage wheels and the rails. Advantages: no modifications required to the track network, can be implemented in cross border traffic, low costs, independent of the electricity network, etc.



Self-monitoring of breakdown in integrated semiconductor devices

The breakdown monitoring which is the object of this invention is achieved in real time by means of a photo diode which is integrated in the semiconductor device. During a breakdown a p-n junction always emits light. It is this light emission that is recorded by the photo diode which is integrated in close proximity of the junction. In response to the strength of the light emission, one can then adjust the voltage or current that is applied to resp. passes through the junction.
Advantages: increased power of transistors, e.g. in oscillator circuits (radar, etc), increased reliability of ICs, increased operating range, protection from destruction.



Key component for the integration of electronic data processing and optical information transmission

Seamless transition between electronic information processing and optical information transfer needs integration of fast optoelectronic components together with the associated electronic components (e.g. drivers, amplifiers, storage components, and microcontrollers) on the same substrate (e.g. silicon-on-insulator, SOI). The novel electro-optical component is based on the rapid change of transmission characteristics of an optical wave guide by means of the application of electric potentials.