Prof Duncan Gregory writes about his team's efforts in developing an improved version of the lithium-ion battery, which will provide more power for a longer duration and be more environmentally sustainable. A group he leads is partnering with the team of senior Indian scientist S Gopukumar.
At the start of the 19th century, Italian physicist and inventor Alessandro Volta, harnessed the power of chemical reactions to generate electricity to create the first battery.
Volta's battery, which he called a 'voltaic pile', used electrodes made of zinc and copper plates sandwiched between pieces of brine-soaked cardboard. The reaction between the metals and the salt water generated electrical current. For the first time, it was possible for people to generate electricity reliably and continuously.
Soon, others refined and improved Volta's work, and batteries became more portable, more powerful, and increasingly commonplace. Today, more than 200 years after the invention of the voltaic pile, batteries play a vital role in modern life, powering a vast range of devices, from personal items such as watches, mobile phones and laptops to more important devices such as communication satellites.
Market research figures released last year predicted that the global market for batteries could be worth $55.4 billion by 2017.
The proliferation of mobile electrical devices has required the development of rechargeable batteries capable of providing more power for longer in smaller packages.
Currently, lithium-ion cells are one of the most popular forms of rechargeable batteries for consumer devices. They are light, can store a large amount of energy relative to their size, and can hold on to their charge effectively over long periods of time.
In these types of batteries, electricity is generated when charged particles (also known as ions) of lithium are passed between electrodes through an electrolyte. Once most of the ions have travelled from the negative to the positive electrode, the battery is discharged; during the charging process, the ions move in the opposite direction and the device can be powered again.
At the University of Glasgow's School of Chemistry, my group is working in partnership with researchers led by S Gopukumar, senior scientist at the CSIR-Central Electrochemical Research Institute in Karaikudi under the CSIR, New Delhi - Royal Society, UK programme to develop an improved version of the lithium-ion battery, which will provide more power for longer and be more environmentally sustainable in its construction.
Tin in batteries?
Graphite is often used as one of the electrodes, known as an anode, in lithium-ion batteries. We're researching the potential of using tin, a metal capable of offering greater energy storage capacity, to replace graphite in a new generation of batteries.
One of the problems with using tin for this purpose is that electrodes of batteries expand and contract during use and charging. Tin electrodes are more likely to crumble and crack under this type of strain than graphite, significantly reducing the battery's total lifespan.
To solve this problem, we're developing an anode constructed from nanoscale wires made from a composite of lithium nitride and tin. We synthesise these wires by grinding lithium nitride and tin together into a very fine powder with a process called ball milling, which is commonly used both in laboratories and industry.
This procedure is relatively cheap, quick and accessible, which means it could easily be used by battery manufacturers. It also requires reasonably low amounts of energy, which could make the process of manufacturing batteries more environmentally-friendly.
We've carefully investigated the process of creating nanoscale wires and believe we have discovered a very effective mix of chemicals and milling techniques to synthesise wires which measure around 500 nanometres in width and around 100 micrometres in length reliably.
Although each wire is tremendously small, lithium ions are considerably smaller, still meaning a vast number of them can collect on a single wire. There is the potential to engineer these wires to even smaller scales.
Effectively, this means that an electrode made from our lithium nitride-tin composite has a relatively huge surface area for lithium ions to collect on and diffuse into. There is also significant space for the wires to expand and contract. These characteristics offer great potential not only to create batteries which are capable of higher capacity but also charge and discharge more quickly and last far longer.
Currently, the composites are far from optimised, but they are already capable of higher capacities than graphite and withstand charging and discharging better than tin itself.
The synthesis and analysis of the new materials are handled in Glasgow. Once identified and characterised, they are sent to collaborators in Karaikudi who prepare cells and test the electrochemical properties of batteries to determine and optimise performance.
There's still a lot of work to be done before we can consider developing these materials further for prototype batteries such as those found in consumer products. However, this approach could be a step forward in the quest to solve the problems of power-hungry mobile devices; our laptops and mobile phones could well run for far longer in the future.
(The writer is Chair of Inorganic Materials at the University of Glasgow.)