Lithium ion batteries: new materials multiply charging capability

September 12, 2014 // By Christoph Hammerschmidt
New materials and a number of detail improvements - that's all it takes to multiply safety and operating life expectancy of lithium ion batteries used to drive electric vehicles. Researchers from German electrical giant Siemens this week introduced a demonstrator of a battery that quadruples the number of charging cycles to 20.000 - hitherto the maximum value was 5000.

The battery is a result of the EiSiBatt research project that aims at developing a safe lithium ion battery technology. The anode of the new battery devised by the Siemens team is not made of graphite but instead of lithium titanate. For the cathode, the researchers replaced the usual lithium metal oxide another material, lithium iron phosphate.

In addition, the researchers from Siemens' Erlangen research centre developed a mathematical model that describes the behaviour of large arrays of hundreds of connected batteries - like those in large energy storages. Also Tesla Motors is utilising a large array of relatively small lithium ion cells in its cars. Numerous measurements and simulations helped the researchers to understand the behaviour and describe it in a complex model that reproduces the electrical, thermal and mechanical behaviour of such battery arrays. The simulations enabled them, among other, to understand the behaviour of energy and power in situations when the battery is used to stabilise an electric grid or to control the frequency of an AC grid.

A team of engineers from Chemnitz-based company Drive Technologies developed a battery management scheme that controls their charging status. This software, derived from a Siemens Simotion control program, can also be assigned to further tasks - for instance it can assume the control if batteries are integrated into a drive compound.

Also participating in the project were chemical company Clariant and battery manufacturer Leclanché. Currently, the researcher have created a demonstrator. It remains to be seen when the technology will be industrialised.