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DEVELOPMENT OF A NEW PROCESSABLE SOLID LI+ ELECTROLYTE FOR ENERGY STORAGE

Objective


The activities of this project focused on the development of new processable polymeric electrolytes for possible applications in lithium rechargeable batteries and new types of supercapacitors.

During the course of the project several different routes were investigated to synthesise new and improved polymeric electrolytes (ionic conducting ORMOCER(r)s) for potential applications in energy conversion and storage devices.
Electrolyte materials have been prepared and employed under both laboratory and industrial conditions to establish handling and processing parameters.
Polyethers with different chain lengths and epoxy- (resp. vinyl-) termination sites were synthesised and attached to organically functionalised oxidic oligomers.

Aside from this main stream work on the electrolyte, efforts were made to demonstrate potential applications of these electrolytes in energy conversion and storage devices. This included the preparation and testing of laboratory scale intercalation cathodes for rechargeable lithium-ion type batteries, as well as the set up of complete rechargeable laboratory batteries and capacitor devices and their testing.

Specific conductivities achieved with pure inorganic-organic polymer electrolytes were in the range of 1E-5 to 1E-4 ohms{-1}cm{-1} at room temperature.
In addition, of crucial importance is the ability of these new electrolyte to bind the manganese oxide particles in the cathode together so that the electrode can be cycled many times before losing too much capacity. This goal was achieved using ORMOCERs without any plasticizers added (more than 900 cycles in comparison to 50 for PEO in the same test), and important and encouraging result, since it indicated that the electrolyte really does succeed in retaining the contact between the cathode particles during cycling - despite the volume changes.
compared with other polymer electrolytes without plasticizers, the developed electrolytes offer a higher conductivity, better thermal stability and easier processing.

The large potential of the new electrolyte is based on its thin film behaviour, offering acceptable conductivity (if thin film technology is possible) without plasticisers, form stability even at higher temperatures and fast UV-curing, conform to large area coating technology.

In view of the envisaged applications of such electrolytes, the addition of plasticizing solvents was thoroughly investigated (no thin film quality electrodes on the market).
By developing suitable methods and by using suitable solvents the conductivity could be increased up to 1E-3 ohms{-1}cm{-1}. This is a reasonable value for technical application allowing the construction of battery and capacitor prototypes.
Final investigations within the project, where polymer foils were metallized and coated with polypyrrol resulting in smooth electrode surfaces (thin film quality) disclose the potential of this new electrolyte (without plasticizer) for thin film batteries and supercaps, if electrodes with thin film quality will be available on the market).
The objective of this European cooperation is to realise a processable inorganic-organic polymer lithium electrolyte for application in all solid state secondary batteries and supercapacitors. This involves the development of improved electrode materials and of an appropriate manufacturing technique for multilayer electrodes/electrolyte foils as well as construction and laboratory and application testing of entire energy storage devices.

The academic partners involved in the programme (one research centre and two universities) have gained sound experience in the development of new materials and in solid state electrochemistry. Two of the four participating industrial companies hold strong market positions in the field of batteries and capacitors while the third enterprise is an end-user of low weight high energy density batteries. The fourth company is well known for its speciality polymers, here electrolytes. All industrial partners are interested to bring the developed systems to production. The new electrolyte will be applicable as stepwise curable thin coating with high adaptability to the manufacturing process for multilayer electrodes/electrolyte combinations that serve as components for new batteries and supercapacitors.

Major environmental benefits result for instance from the fact that the new lithium batteries proposed to be developed can replace common Ni/Cd cells. Improved supercapacitors will among others have great impact on the development of electric cars.

This project is of particular strategic importance for European industry in order to be able to compete with Japanese and American developments. The innovative character is especially expressed in the fact that there are no secondary lithium cells on the market.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

FRAUNHOFER GESELLSCHAFT ZUR FORDERUNG DER ANGEWANDTEN FORSCHUNG E.V.*
Address
Neunerplatz 2
97082 Wuerzburg
Germany

Participants (5)

Eniricerche SpA
Italy
Address
Via Felice Maritano 26
20097 San Donato Milanese
SONNENSCHEIN LITHIUM GMBH
Germany
Address
Industriestraße 22
6470 Büdingen
THOMSON LCC
France
Address
3 Rue Du Stade
21250 Seurre
TU DENMARK
Denmark
Address
Building 309
2800 Lyngby
Teltag
United Kingdom