Battery research striving to make batteries more durable
A research project sparked by enterprise needs
Two research groups from the Aalto University School of Chemical Technology are searching for ways in which to make lithium-ion batteries safer and more resistant to moisture and temperatures. The materials chosen can influence these properties.
Reactions in traditional batteries, in which cobalt oxides are the positive electrode material, are very exothermic i.e. heat-producing. If these traditional batteries malfunction, the electrolyte may begin to vaporise, causing the battery to explode. This is why batteries have a management system that prevents overcharging and over-discharging.
Batteries contain sensitive electrotechnology, which means that different parts of a battery may break in spite of the safety systems in place. Due to the greater amount of energy involved, the consequences of malfunctions in batteries such as car batteries are more severe than those produced by a malfunction of a mobile phone or laptop battery. For this reason it is important to develop and use safer and more durable materials.
Compared to traditional lead-acid batteries, lithium-ion batteries have the advantage of being light in weight. Lithium is one of the lightest elements, meaning that batteries using lithium can be made lighter and smaller in volume.
Lithium-ion batteries do not function at low temperatures. Researchers are now looking for a solution with which to expand the range of a lithium-ion battery’s operating temperature. This is important as especially car batteries must also be reliable in cold conditions. A battery is an expensive component and as such should last be a long-term investment. Batteries must endure as many charge/discharge cycles as possible without sustaining significant changes.
Improved performance through doping alloys
It has been established that the properties of lithium iron phosphate make it safer than traditional electrode materials. However, electrochemical reactions are slow when lithium iron phosphate is used. Researchers have had to investigate whether the factor causing the limited reaction is the electron transfer or perhaps lithium-ion’s migration in the material. The research group is looking to solve these problems by altering the properties of materials.
Researchers have syntehesized a series of materials in which the properties of lithium iron phosphate have been systematically changed by replacing iron with small amounts of other elements and studying performance of this series at low temperatures. This process is also called doping.
In addition to manganese doping, researchers intend to change the share of different materials in the nickel-cobalt-manganese series. Their objective is to study the chemistry that causes changes in performance; in other words, whether the change is a result of bond energy or bond distance.
A research project initiated by the business world
The research project was initiated some three years ago due to requests from companies for assistance with manufacturing materials for lithium-ion batteries and the printing technology for electrodes.
A research group in inorganic chemistry, headed by Academy Professor Maarit Karppinen, has placed its focus on studying and producing the materials needed for production of batteries, while a research group in physical chemistry, headed by Docent Tanja Kallio, is studying and developing the electrochemical properties of batteries.
The group of researchers has been working for some two years to reach the international level of the field. The university has acquired the equipment needed for this research, and the international connections of the women heading the research project have been put to use. Before becoming a professor at the Helsinki University of Technology, Dr.. Karppinen worked in Japan and has ties to Chinese and Japanese experts as well as American material scientists. Finnish postgraduate students have had the opportunity to travel abroad to work with and learn from these experts.
Dr. Kallio has connections within the KTH Royal Institute of Technology in Stockholm and J. Heyrovsky Institute of Physical Chemistry in Prague. Cooperation with the Swedish university has brought new expertise to this line of research.
The research project will continue through next year. Funding for possible further research will be applied for from the European Union and Tekes, the Finnish Funding Agency for Technology and Innovation.
Academy Professor Maarit Karppinen, maarit.karppinen [at] aalto [dot] fi
Docent Tanja Kallio, tanja.kallio [at] aalto [dot] fi