Making batteries safer and longer-lasting
Almost everyone who uses a mobile device would agree that a major bugbear is invariably the relatively short life of the battery. While a majority of users try to address the issue by rushing to the nearest charging points at hotels or airports, others carry power banks, adding to the weight of their handbags.
To make matters worse, airlines do not allow power banks and batteries to be checked in while flying, fearing that the batteries could explode and create a fire hazard, the Samsung Note 7 episode and recent recall of some Hewlett-Packard notebooks (to avoid a potential battery explosion) being cases in point.
Moreover, with Apple Inc. admitting that it throttled the speed of older iPhone models with ageing batteries (Android phones have a similar problem), there is again a focus on how poor battery life can sour a good digital experience.
Researchers have tried to address the twin issues of making lithium-ion batteries safer and longer-lasting. Sometimes they have tweaked the materials, or experimented with altogether new materials. At other times, they have devised new prototypes.
To begin with, a lithium-ion battery comprises a negative electrode (anode) that typically uses lithium and a positive electrode (cathode) that traditionally uses graphite, kept apart by a separator. When connected to a device, the rechargeable lithium-ion batteries work because of a liquid called an electrolyte which transports the lithium ions back and forth between the anode and the cathode, causing an electrochemical reaction.
Researchers at the University of Maryland and the US Army Research Laboratory say they have developed a lithium-ion battery that uses a water-salt solution as its electrolyte and can work for household electronics such as laptop computers, “without the fire and explosive risks associated with some commercially available non-aqueous lithium-ion batteries”. Their work was published on 6 September in Joule, biomedical journal publisher Cell Press’s new interdisciplinary energy journal.
Researchers from the Swiss Federal Laboratories for Materials Science and Technology (Empa), and the University of Geneva (Unige), Switzerland too, have devised a new battery prototype, known as “all-solid-state”. This battery, the researchers said in a 23 November press statement, has the potential to store more energy while maintaining high safety and reliability levels. Furthermore, the battery is based on sodium, a cheap alternative to lithium. The research was published in the journal Energy And Environmental Science.
The battery developed by Empa and Unige researchers uses a solid rather than a liquid electrolyte that blocks the formation of dendrites (microscopic growths of lithium in the battery that can reduce its life and cause short circuits). This makes it possible to store more energy while guaranteeing safety, the researchers said. The battery, they admitted, still has to be tested at room temperature.
Meanwhile, researchers at the University of California, Riverside’s Bourns College of Engineering, used waste glass bottles and a “low-cost chemical process to create nanosilicon anodes for high-performance lithium-ion batteries”, according to research published in April in the Nature journal, Scientific Reports.
In July 2014, University of California researchers had announced that they were working on using beach sand to develop a longer-lasting lithium-ion battery.
A team, led by scientists at the US department of energy’s Brookhaven National Laboratory, now claims to have uncovered a major step towards improving the battery life of consumer electronics. In their article, published on 12 January in the journal Science Advances, the researchers point out that every lithium-ion battery contains particles whose atoms are arranged in a lattice—a periodic structure with gaps between the atoms. When a lithium-ion battery supplies electricity, lithium ions flow into empty sites in the atomic lattice. However, the researchers noticed that concentration of lithium did not increase continuously in the lattice, as they had expected. Rather, the uneven movement of lithium strains the structure of the active materials in batteries.
The researchers hope these findings will help them develop batteries that can charge faster and last longer.
Cutting Edge is a monthly column that explores the melding of science and technology.