Add just a pinch of salt for longer battery life (Day 92)
27th August 2014
One of the major considerations when making, and buying, modern consumer products is battery life. Cheaper products generally have short battery lives. You'll pay considerably more for better performance, but even high specification smartphones barely last more than half a day according to a recent test.
Most portable consumer electronics, like mobile phones and laptop computers, will have Lithium-ion batteries because of their high power-to-weight ratio, high energy efficiency, good high-temperature performance, and low self-discharge.
However good, relatively, Lithium-ion batteries are, their performance declines over time with 'dendrites' one of the major causes.
The so-called dendrite problem has been troubling lithium battery technology for years. Over several charge/discharge cycles, microscopic particles called dendrites form on the electrode surface and spread, causing short circuits and rapid overheating
However, chemical engineers at Cornell University have found that adding certain halide salts to liquid electrolytes spontaneously creates nanostructured surface coatings on a lithium battery anode that hinder the development of detrimental dendritic structures that grow within the battery cell.
The discovery opens the way potentially to extend the daily cycle life of a rechargeable lithium battery by up to a factor of ten.
The traditional 'management' of the dendrite has been through the careful design of the electrolyte and battery operating condition.
However, the Cornell team - led by Lynden Archer, the William C. Hooey director and professor of chemical and biomolecular engineering - took a different approach.
They went to "density functional theory" and "continuum analysis" – forms of chemical modelling – to examine the stability of metal electrodeposition for answers. This effort led to the conclusion that infusing simple liquid electrolytes reinforced with halogenated salt blends in a nanoporous host material holds the long-sought solution.
The result: Lithium metal based batteries that exhibit stable long-term charge/recharge cycling at room temperature, with no symptoms of instability over hundreds of cycles and thousands of operating hours, the researchers reported.
Lynden said: "We had conflicting insight from two theories under development in the group and by theorists in the Cornell physics department, which suggested that a nanostructured metal halide coating on the anode could help a little – or a lot – in controlling the formation of dendrites. As it turns out, they work spectacularly well in solving what is widely considered a grand-challenge problem in the field".
Lynden also believes the breakthrough will result in safer batteries by reducing internal shorts caused by the dendritic structures which can lead to overheating.
When you consider that around half the world's population own a mobile phone, that's a lot of batteries and people to please. Does chemical engineering matter? You bet it does!