Everyday use of smartphones and other portable devices has shown us that Li-ion batteries are struggling to keep up with the power demands of today’s consumer electronics. When we develop a wish list for batteries for all our technologies (phones, tablets, wearable technologies, electric vehicles, gadgets etc.) we envision light, safe, environmentally friendly batteries which are capable of fast charging with high capacities and long cycle life. It is a demanding list, but these goals are firmly on research agendas for many scientists worldwide. Often, finding a material that is abundant, non-toxic and safe, that outperforms its counterparts with fewer and milder processing or additives, is a difficult challenge in the search for better batteries. Recently, a breakthrough has been reported using a common material fashioned in an uncommon way, which provides an ultra-long life Li-ion battery.
The research supported by Science Foundation Ireland was undertaken by David McNulty, a postdoctoral research and Colm O’Dwyer, Principal Investigator at University College Cork in Ireland. The researchers have developed a method that allows titanium dioxide (TiO2), a naturally occurring mineral which is also used as a UV absorbing material in sunscreen creams, to create one of the longest life Li-ion battery anode materials.
The breakthrough provides a material made into an ordered porous architecture to ensure the material efficiently charges and discharges for over 5,000 cycles, without any significant capacity fading. This 3D arrangement of nanoparticles of the rutile phase of titanium dioxide is called an ‘inverse opal’ and is formed by infilling artificial opals made in the laboratory, with the active battery material. Inverse opal structures are naturally found in nature. These periodically porous structures make up the colourful, iridescent parts of butterfly wings, peacock feathers, the exo-skeletal structures of weevils, and the sea mouse, to name a few. By creating porous materials in an ordered fashion, nature provides new functionality. The team at UCC adapted this approach to investigate electrochemical phenomena - in this case, high performance Li-ion battery materials.
Current Li-ion technology uses materials that are randomly mixed with polymers (for binding) and conductive carbons (for electrical conductivity). As the projected need for Li-ion technologies increases for electric vehicle use, consumer electronics, and in the proliferation of off-grid wireless communications for 5G, research and development is striving to find non-critical, earth abundant materials that have excellent performance and last a long time. Binders that are non-toxic and do not contain fluorine are more eco-friendly and can be processed more safely. In this finding, for battery technology, the TiO2material performs without any of these additives, and the entire battery material is green, abundantly available, non-toxic, fluorine-free and devoid of critical raw materials.
The simplicity of the breakthrough is remarkable, as it mitigates some technological and processing issues for battery materials. By networking active nanoparticles in an open-worked porous geometry, long life Li-ion battery electrodes are possible using just the active material.