Cost-effective manufacture of lithium batteries
Compared with other electrochemical storage systems, lithium-ion batteries have high energy efficiencies, high energy densities and long service lives. They are therefore the first choice for many mobile applications. However, they are still not used very much as stationary storage systems and are comparatively expensive. It is intended that environmentally friendly and cost-effective production processes for the battery cells and storage systems shall change that.
|Project status||Testing the cells|
|Typical system size – energy [MWh]||0.01 to 0.1|
|Volumetric energy density [Wh/l]||275 Wh/l or 130 Wh/l|
|Gravimetric energy density [Wh/kg]||130 Wh/kg or 60 Wh/kg|
|Gravimetric power density [Wh/kg]||500 W/kg|
|Cycle strength (80% discharge depth)||6,000 – 16,000|
|Service life of the system (1 cycle/day)||1 to 10 cycles/day|
|Typical discharge time||0.25 to 10 h|
|Example application fields||Stationary energy storage systems for domestic and grid integration|
|Project duration||March 2015 until March 2018|
Lithium-ion battery cells have become established as energy storage devices in the drive train of vehicles as well as in notebooks, mobile phones and radios. The cells, which were developed for mobile applications, are frequently also found in stationary storage systems for domestic and grid applications due to the lack of alternatives. However, because they are not optimised for these uses, the cells often do not have the characteristics required such as longevity, safety, environmental friendliness and low manufacturing costs.
In the LiSta project, scientists are developing basic principles for specialised energy storage devices that are cost-effective, environmentally friendly and durable, and thus more suitable for stationary applications. For this purpose, they are investigating materials, cell and storage designs as well as production processes and analytical methods for determining the ageing.
In a first step, the project partners are analysing the requirements for stationary storage systems. This will enable them to derive the performance characteristics that the battery cells will need to meet. The partners are pursuing an integrated research approach that covers all essential areas of storage research, ranging from the application testing, construction, design and material selection to the manufacturing process and fault analysis.
In order to make the investments economically justifiable, the scientists are striving to achieve a service life for the energy storage systems that exceeds 20 years. Depending on the application, this corresponds to between 6,000 and 16,000 full-cycle equivalents.
Environmentally friendly design
The requirements for the storage systems are determined by the cell chemistry. The scientists are developing environmentally friendly production processes where they can dispense, for example, with substances that are harmful to health and the environment, such as organic solvents. The cell structure is intended to enable process-optimal production of storage systems and battery cells. This structure needs to prove itself in ageing tests and is being continually improved. Suitable machines and tools are being constructed and procured for researching the production methods.
Basic investigations were carried out in the second project year. The analysis and manufacturing methods were successfully evaluated. The findings during the testing of the cells are currently being verified and cells prepared for storage units.
- Drafting of specifications / requirement definition for storage devices and cells
- Definition of the most important manufacturing steps and load specification for the system design
- Construction of test fields / test facilities
- Evaluation of the analytical methods for investigating the ageing
- Material research begins
- Research on cell casings and safety elements begins
- Research on battery cell manufacturing methods
- Research on optimal storage designs begins
- Testing of initial materials; cell designs and manufacturing methods
- Completion of the research on basic process parameters
- Implementation in research test facility begins
- Evaluation of initial samples in storage units
- Analysis of weaknesses and ageing effects
- Test phase for cells from the research test line
- Assembly of storage modules and storage devices
- Testing of storage devices and cells under realistic conditions
- Analysis of properties and ageing effects
- Aalen University of Applied Sciences is studying methods for analysing the ageing mechanisms and fundamentals for designing optimal cell housings that have high longevity. The cells created by VW-VM are therefore being examined for weaknesses and ageing effects. Long-life cell case variants are being researched, which will be used in direct testing at VW-VM. An important focus is on creating permanently stable, electrically insulating bushings for the arresters.
- VARTA Storage is researching storage designs and manufacturing methods for these systems, whereby the battery cells are being integrated by the partner VWVM and tested in realistic tests.
- VW-VM Forschungsgesellschaft is researching materials, cell designs and production methods for manufacturing particularly safe and long-lasting battery cells for stationary storage systems. Active materials include lithium iron phosphate, lithium titanium oxide and carbon materials. An essential aspect in this regard is environmentally friendly processing. As part of the battery cell research, it is intended to identify and test long-lasting and robust cell designs as well as cost-effective production methods.