Enhancing performance of lithium batteries
Improving lithium energy storage systems is the aim of the EU-funded ALISTORE (Advanced lithium energy storage systems based on the use of nano-powders and nano-composite electrodes/electrolytes) Network of Excellence. 'It is clear that electrical energy storage is a critical issue for the new energy economy and one for which rechargeable lithium batteries, alongside other technologies, have an important potential impact,' the project partners agree. The rechargeable lithium battery was first introduced in 1990, and was an important breakthrough in energy storage. Today it can be found in many devices, including mobile phones, digital cameras, laptops and even electric cars. However, their lifespan and performance, in addition to technical problems, mean that they have fallen short of meeting technological demands. According to researchers and developers within the ALISTORE project, nano-materials could offer a solution and 'have the potential to revolutionise battery design'. First, though, the basic problem must be understood, which is why Dr Wolfgang Dreyer, a physicist at the German Weierstraß Institute for Applied Analysis and Stochastics (WIAS) has been asked to develop a mathematical model of the electrochemical processes that take place inside a lithium battery. In principle, a lithium battery contains countless nano-balls made up of iron phosphate, which are gathered around the negative pole. The positive pole, on the other hand, consists of lithium or lithium alloys. Now, when power is taken from the battery, lithium ions move towards the negative pole, and iron phosphate balls swell. When the battery is recharged, the lithium ions move back to the positive pole. The technical problem is created by an imbalance between power input and power output, shows data provided by Slovenian colleagues on electrochemical processes, a process called hysteresis. Dr Dreyer is sure that an exact model could help to cut down on expensive experiments and thus save time and money, as only very promising experiments will still be carried out. In the end, improvements will be fundamental, he says: Hystersis will decrease as will charge times while charge density will increase considerably.