Fertigung von Batteriezellen stellt hohe Anforderungen an den Sauberraum
Raid into frontiers of physics: Production of a new Akku generation for electric cars permitted only a maximum air humidity of 2 ProzentSeit about twenty years are vehicles with electric drive in the meantime on the market. The fact that they did not become generally accepted despite their energy efficiency and ecology so far yet wide is particularly because of the limited range of the electric vehicles: In the available batteries only a comparatively small energy quantity can be stored and carried. In order to be able to put with the electric cars also longer distances back, the energy cells must become therefore easier and more long-lived. Volkswagen and Varta Microbattery created a common research association in order to examine and increase the efficiency of lithium ion Akkus for the employment in vehicles. However the manufacturing of the sensitive battery cells makes also high demands against the production environment. The system space farmer Nerling had to go thereby to the borders of the physically possible one and to develop a clean area with a constant air humidity of maximally 2 per cent. � usually the relative dampness for clean areas is with 40 to 60 per cent and thus in the comfort range for humans �, explains Olaf Nerling, managing director of the Nerling system area GmbH. Within the automobile range against it already 35 per cent are required, in order to exclude flight rust danger by the air humidity. During the processing of to types of dust feingemahlenen active substances in pharmaceutical industry the relative space dampness may amount to even only 10 per cent. � at present highest requirements come however from electro-technology �, report Nerling. � in the case of the manufacturing of lithium ion battery cells with Volkswagen Varta Microbattery research association ltd. & CO kg is required with values of at the most 2 per cent of relative dampness an extreme dryness. � humidity with the production worsens achievement BatterienDas a goal of co-operation between Volkswagen and Varta Microbattery consists of improving by the development of own lithium ion cells the reliability, longevity and power density of the batteries for vehicles with electric drive. � our vision is it, by the bundling of many also small innovations Germany � particularly in relation to the Asian market � as production location to make internationally competitive �, says Professor Dr. Werner writer, managing director Volkswagen Varta Microbattery research association ltd. & CO. Kg. With the production of such battery cells the used raw materials are exposed to the influences from the environment. � the pastes for the electrodes are applied on metallic transparencies, afterwards dried, kalandriert and cut �, explain to writer the basic principle of the production. � these electrode foils are wound thereafter together with a separator. For that electrode-wind forms then the core of the battery cell. � if the chemicals with the processing in the glazing calender (Kalander) humidity are suspended, change them however their characteristics. � the production area must be extremely drying, because otherwise the quality and reliability of the battery cell suffer from it �, say writers. � in addition the life span of the battery shortens, if it were exposed to a too high space dampness with the production process. � adsorption drying as new procedure of the KlimatechnikDa with conventional air condition technology a so low space dampness of at the most 2 per cent not to reach is, used Nerling as well as a cooperation partner the still relatively new procedure of the adsorption drying. Dehumidifying by a rotor, which consists of a wavy fibre glass structure, the silica-gel as sorbents contains been made here. � the processing air is blown for dehumidifying by the rotor, delivers thereby its humidity to the sorbent and flows as dry air into the clean area �, describes the managing director. � by the turn within a separated range hot air is then supplied to the rotor, which removes and into outside air omits the accumulated humidity for the rotor. � a further challenge for the permanent air dehumidification placed itself in the determination of the accurate humidity. � we push here into frontiers of the physically possible one forwards �, say Nerling. � usual sensors can seize as small values less as 2 per cent relative dampness and no more. � the moisture meters would have to be able to detect quasi individual water molecules here. Therefore to another measuring technique one fell back: The humidity in the clean area is determined now over special dew point temperature feelers. The relative dampness of 2 per cent therefore corresponds to a dew point temperature of -30�C. � with this alternative measuring method a dryness up to a dew point can be determined by -90�C �, so Nerling. � in a next project we will try for the first time to in this way reach a relative dampness of under a per cent and/or a dew point from -60 degrees to. � complete solution inclusive KranDer clean area of 15,5 x 5.6 meters installed in one resounds Volkswagen Varta Microbattery research association in Ellwangen on production conditions and cultivated by means of a connecting door to an already existing drying room. Further requirements were an ambient temperature of 20�C and a cleanliness after pure class of area ISO 8. � in addition played apart from the cost factor also short delivery times and date loyalty an important role, there we the times for the delivery and list of the further production plants to absolutely keep had �, for the agency of the Systemraumbauers of Baden-Wuerttemberg were so writer decisive for Volkswagen Varta Microbattery research association its comprehensive know-how in all ranges. Thus for example 10 a ton crane in the clean area was needed, with which the calender roll for revision purposes can be dug. � the company Nerling was the only offerer, that us a ready for occupancy complete solution from clean area, air condition technology and crane to supply could �, justifies writer the decision. Since the glazing calender has the largest dimensions of the trades in the clean area, its height had to amount to here over 5.5 meters. In order to avoid an unused clearance volume over the remaining surface and thus unnecessary costs of the air conditioning, the room height was designed to a large extent for 3.3 meters and only over the Kalander a cathedral established. Aluminum tear sheet metal prevents damage by electrostatic loadings � a further problem with only 2 per cent of relative dampness is that over air and a usual PVC ground no electrostatic loadings can be derived more �, explain Nerling. Then exist however the danger that it comes with the manipulation of press control to the spark estimate and the equipment is damaged. Remedy creates here vapor diffusion-close floor with aluminum tear sheet metal, developed of system space farmer particularly for it. This floor mat guarantees also with extremely low dampness degrees the derivative of the loads. Likewise of central importance for the automatic constant of the space dampness is the tightness of the entire plant. The external walls and windows of the clean area are adapted accurately together in order to exclude air cracks to the surrounding workshop. As entrance there is a material and an air-lock for persons, which are equipped with mutually locked doors, so that no air humidity can penetrate. The second door to the interior opens thereby only after the so-called rinsing time, thus if the air conditioning system withdrawed the dampness. In this manufacturing environment co-ordinated with the special requirements in the meantime the research Joint of the venture starts for the optimization of battery cell chemistry and manufacturing methodology. The cooperative project of Volkswagen and Varta Microbattery is first on four years put on and during this time of the Federal Ministry for economics and technology is promoted. � if the interest in the electrical mobility in our society further increases and the pilot project successfully runs, strives we a large-scale installation for the serial production of such battery cells for electric cars on �, means writers with view into the future. Picture: Nerling system area GmbH
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