keeping lithium batteries from burning - small lithium ion battery
In January 7-14, five Boeing 787 Dreamliner accidents occurred around the world, raising concerns about the design and installation of safety measures.
The investigation shows lithium is the culprit. ion (Li)batteries on-
Get on the plane.
They were burned, started smoke detectors and caused an emergency landing or stranding.
The main cause of burns
Ups is a problem called heat out of control.
In each charging process, in the lithium battery
There is a small amount of charge loss in the discharge cycle, just as the electron evades the desired electro-chemical reaction.
"The number of losses is a geometric series.
It has a very low starting point, but it has accumulated very quickly in thousands of cycles, "explained Dr.
Venkat Viswanathan will be an assistant professor of mechanical engineering at Carnegie Mellon University this fall.
"Because this charge goes into another reaction, heat is generated.
So in each cycle the battery gets hotter and the performance is worse.
As the temperature rises, any flammable part begins to burn.
One of them is the electrolyte, the substance responsible for transmitting the charge inside the battery.
Hydrocarbon carbonate is a common electrolyte in lithium batteries and has high flammable properties. Finding a non-
Flammable alternatives are difficult because newcomers must be as good as carbonated grease in other ways in order not to affect the performance of the battery, especially since they are also used for renewable energy
Energy storage and electric vehicles. “Non-
The carbonated-based materials studied in the literature rarely report ion conductivity similar to these carbonated roots, "said Dominic Huang, a graduate student at the University of North Carolina (UNC), in an email.
In an accidental turn of events, alternative candidates lurking at the bottom of the boat may be found.
Serendipitouusjoseph DeSimone, a professor of chemistry at the University of North Carolina, is working on perf (PFPE)
When he realized that the chemical properties of marine organisms are similar to the electrolytic quality in lithium batteries, the polymer that prevents marine organisms from sticking to the bottom of the boat.
His team did further research in the lab and found that lithium salts can be dissolved. a prerequisite.
Most polymers cannot do this.
In the experiment, the electrolyte is sandwiched between two lithium foil electrodes and the battery is charged differently
Discharge rate at different temperatures.
Under these conditions, Dr.
Nitash Balsara, professor of chemical and biological molecular engineering at the University of California, Berkeley, said in an email, "the current density is much lower than the laptop and cell phone batteries, but it is equivalent to the current density required for backup of fixed energy such as solar power plants. ". Dr.
Balsara and his team studied the transmission of lithium ions in batteries.
A very high number of transfers0. 91-1.
0, not the previous 0. 5 —
There are also reports.
According to the Lady
Wong, "the number of moves of the ion is the fraction of the total conductivity that the ion carries during charging and discharging.
Therefore, the value close to unity means a better charge transfer.
According to their paper, one reason this may happen is that fluorine in PFPE promotes oxygen atoms in PFPE to become reluctant electronic donors, allowing positive lithium ions to pass through it more freely.
The researchers also reported that PFPE had a lower electro-chemical polarization of hydrocarbon carbonates, meaning a higher guide voltage for each cycle.
The flammable problem may have been solved, but PFPE-
The battery is still a way to go before it goes public.
While the heat generated is proportional to the flammable nature of the electrolyte, the researchers will now check whether PFPE will produce other undesirable features during the cycle.
Also cost: PFPE cost at least 10-
Ten times more than carbonated hydrocarbons. However, Ms.
Wong hopes they will become cheaper as they are easier to produce and remain stable in the presence of moisture and oxygen.
While these batteries are ubiquitous in portable electronics due to improved fault protection measures, there is a larger background search for viable alternative electrolyte.
In fact, PFPE is not even the first polymer to be considered, although it is the first non-combustible polymer with a performance comparable to that of carbonated hydrocarbons.
A collaborative project of American universities and research centers called the Joint Energy Storage Research Center (JCESR)
Established in 2013.
According to the doctor
One of the goals of JCESR is to write a "electrolyte genome": to build a database based on the nature of all known electrolyte, so that it is easier for scientists and manufacturers to find substances that best suit their research or product needs.