Waterloo chemists develop promising cheap, sustainable grid energy storage

Friday, August 26, 2016

Solar panel and wind turbines in a field.

Waterloo chemists have developed a safe, high-capacity zinc-ion battery that costs half the price of current lithium-ion batteries, yet lasts twice as long.

In a fundamental rethink of lithium-ion technology, University Research Professor Linda Nazar and her colleagues have created a system ideal for large-scale electricity storage which will enable whole communities to shift away from traditional power plants and into renewable solar and wind energy production.

Better still, the battery uses safe non-toxic materials such as zinc – the metal used to make American pennies – and the positive electrode material can be easily manufactured using a microwave.

The world is ripe for grid energy storage, said Nazar, a Canada Research Chair in Solid State Energy Materials in the Department of Chemistry. The aqueous zinc ion battery we’ve developed is perfect for this type of application because it’s relatively inexpensive and it’s inherently safe.

Her team’s results as well as the battery’s innovative fabrication method were published this week in the prestigious journal Nature Energy.

Their battery with a water-based electrolyte, a pillared vanadium oxide positive electrode and a metallic zinc negative electrode vastly out performs previous unsuccessful attempts at using inexpensive zinc in a rechargeable intercalation cell. The battery uses safe, non-flammable, non-toxic materials and a pH-neutral, water-based salt as the electrolyte that does not cause dendrite growth.

Materials and battery types that were unmarketable ten years ago are now seeing a renaissance in research attention due to the carbon reduction targets adopted under the recent Paris Agreement. The $1 billion global market in energy storage is expected to grow to $25 billion in just ten years.

The focus used to be on minimizing size and weight for the portable electronics market and cars, said the paper’s first author Dr. Dipan Kundu, a postdoctoral fellow in Nazar’s lab. Grid storage needs a different kind of battery and that’s given us license to look into different materials.

The battery generates electricity through a reversible process called intercalation where positively charged zinc ions travel from the zinc metal anode and insert into the cathode made of vanadium oxide nanosheets. The flow of electrons gravitates towards the now positively charged cathode creating an electrical current.

Water in the electrolyte not only facilitates the movement of zinc ions, it also swells the space between the sheets, like pillars on a wedding cake, giving the zinc just enough room to enter and leave the cathode structure as the battery cycles. The electrode material’s nano-scale distances and liquid electrolyte also improve its cycling life and response times.

And unlike lithium, zinc is non-reactive, so the aqueous zinc ion battery can use a pure zinc metal anode – a much more energy dense construction than lithium ion batteries that need a stable graphite anode to house a limited number of lithium ions.

The bonus for manufacturers, however, is that this battery can be constructed without special conditions, such as ultra-low humidity, dust control, and flammable materials handling required for lithium ion batteries. The vanadium-oxide nanosheets for the cathode are created using a very fast, scalable microwave method

Together with researchers at the Joint Center for Energy Storage Research in the USA, Nazar’s team is also investigating multivalent ion intercalation batteries based on Mg2+ in non-aqueous electrolytes. They were the first to report highly reversible Mg cycling in the TiS2 thiospinel and layered sulfides, which represent the first new highly functional Mg insertion materials reported in over 15 years since the seminal publication in Nature in 2000. Their papers appeared in Energy & Environmental Science and ACS Energy Letters earlier this year.