Stanford boosts century-old battery tech
Graphene speeds up ‘Edison battery’
A group of Stanford University scientists is claiming a breakthrough using graphene that would bring nickel-iron batteries into the modern world.
Originally an invention of Thomas Edison, nickel-iron batteries are durable but slow, both for charging and discharging. Although they only lasted in their original application – electric vehicles – until the 1920s, the technology lasted much longer as a backup technology for railroad uses, as well as storing surplus energy in the solar and wind-turbine power sectors.
The batteries are simple – iron anode and nickel cathodes bathed in an alkaline solution – and use abundant and relatively non-toxic materials.
Now, according to Stanford graduate student Hailiang Wang, the new research has “increased the charging and discharging rate by nearly 1,000 times”.
The speed boost comes from applying the world’s current favourite wonderstuff, graphene, to both the anode and cathode. The nickel hydroxide cathodes are grown onto carbon nanotubes consisting of ten concentric graphene sheets, while iron oxide anodes are grown onto graphene sheets.
Stanford’s announcement explains that this process results in strong bonding between the metals and the graphene.
“Coupling the nickel and iron particles to the carbon substrate allows electrical charges to move quickly between the electrodes and the outside circuit,” according to chemistry professor Hongjie Dai.
“The result is an ultrafast version of the nickel-iron battery that's capable of charging and discharging in seconds.”
While the nickel-iron battery has low energy density, the Stanford group believes it would be used in conjunction with lithium-ion batteries in electric vehicles. The high charge-discharge rate would provide a boost when needed, recharging quickly from regenerative braking.
Their work has been published in Nature Communications. ®
That's what I get for replying in the early hours of the morning using info I haven't actively used in 15 yrs.
Being corrected instantly is one of the reasons I love this place. No, seriously.
Now where's me coffee?
Flock Kroes is perfectly correct, Martin 71 got it wrong. The voltage/charge relationship is indeed linear, far more so than a battery. The logarithmic capacitor behaviour is voltage/time when connected across a constant resistance, in which case the current (charge moved per unit time) is no longer a constant but varies lineally as the voltage across the capacitor varies.
The basic formula for a capacitor is: Charge = Capacitance x Voltage. A linear relationship, not logarithmic. Batteries have a more complicated relationship that changes when a resource becomes limited and when the temperature changes because of the charge or discharge current.