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Pacific Northwest National Laboratory (PNNL)

Scientists develop lithium-metal battery with 600-cycle life

Thu, 07/15/2021 - 15:27 -- paul Crompton
lithium metal pile

Scientists at the U.S. Department of Energy’s Pacific Northwest National Laboratory (PNNL) have created a lithium-metal battery that lasts for 600 cycles.

Lithium-metal batteries hold almost twice the energy, are safer and lighter than lithium-ion, but still have some way to go to match the 1,000 cycle life.

The PNNL team replaced anodes with thin strips of lithium— 20 microns wide— to produce a lithium-metal pouch battery with an energy density of 350Wh/kg.

After 600 cycles, the battery retained 76% of its initial capacity. 

The work was published in the journal Nature Energy.

 Jie Xiao, who along with Jun Liu, the director of the Battery500 Consortium, is a corresponding author of the paper, said: “Many people have thought that thicker lithium would enable the battery to cycle longer, but that is not always true. 

“There is an optimised thickness for each lithium-metal battery depending on its cell energy and design.”

Four years ago, an experimental lithium-metal battery could operate for 50 cycles, that was increased to 200 two years ago by the PNNL team. 

Making the battery last longer

The scientists found that thicker strips contribute directly to battery failure due to reactions around the solid electrolyte interphase (SEI).

The SEI allows certain lithium ions to pass through, but limits unwanted chemical reactions that reduce battery performance and accelerate cell failure. 

A primary goal for researchers was to reduce unwanted side reactions between the electrolyte and the lithium metal.

The team found that thinner lithium strips are adept at creating “good SEI”, while thicker strips have a higher chance of contributing to “harmful SEI”. 

In their paper, the researchers use the terms “wet SEI” and “dry SEI”— the former retaining contact between the liquid electrolyte and the anode, making important electrochemical reactions possible. 

But in the dry version, the liquid electrolyte doesn’t reach all of the lithium because the thick lithium strips means the electrolyte needs to flow into deeper pockets of the lithium, and as it does so, it leaves other portions of the lithium dry. 

Today’s electric vehicle batteries are aroud 200-250Wh/kg; Battery500 is aiming for a cell level of 500Wh/kg.

A report from PNNL noted the combination offers the enticing prospect of an electric vehicle that would be lighter and go much farther on a single charge. 

The report noted: “It’s a big step forward for a promising technology, but lithium-metal technology is not yet ready for prime time. 

“While the lithium-ion batteries used in electric vehicles today hold less energy, they last longer, typically at least 1,000 cycles. But vehicles won’t go as far on one charge as they would with an effective lithium-metal battery.”

The research was done through DOE’s Innovation Center for Battery500 Consortium, a multi-institution effort led by PNNL to develop electric vehicle batteries.

PNNL leads the consortium and is responsible for integrating the latest advances from partner institutions into devices known as high-energy pouch cells and demonstrating improved performance under realistic conditions.

Battery500 consortium 

BEST first reported on the Battery500 consortium in 2016 when a consortium of US companies received $50million in federal funding to develop next generation lithium-metal batteries.

The firms received up to $10 million a year over five years from the Department of Energy's Office of Energy Efficiency and Renewable Energy.

Last month, BEST reported how a team from Harvard University in the US had designed a lithium-metal solid-state battery that could be cycled at least 10,000 times.

The researchers paired a multilayer battery that sandwiches materials of varying stabilities between the anode and cathode with a commercial, high energy density cathode material.

Responding to Harvard's research, a PNNL spokesman told BEST: "The report that you cite analyses the energy of just one component of a battery— the cathode only. The report from PNNL discusses the energy of the entire battery. This is a more relevant measure of battery function.

"Another way to put it is that the cell level energy measured by the PNNL team is based on the entire pouch cell, while the measure in the other report is based on the cathode only. An interesting question would be to know the cell level energy if the Harvard team had converted its energy based on the weight of the whole cell."

 
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Zinc graphite aqueous dual-ion battery paves way for safer grid-energy storage

Tue, 03/02/2021 - 10:18 -- Vic
Ismael Rodríguez Pérez PNNL

Pacific Northwest National Laboratory (PNNL) materials scientist Ismael Rodríguez Pérez has formulated a new type of cell chemistry for zinc batteries to double the voltage of aqueous zinc batteries.

Until now, the use of graphite as a cathode has been limited by the narrow electrochemical stability of water, which caps out at 1.23 volts. To increase the performance, Pérez and his team gave the aqueous electrolyte an extra boost by using a highly concentrated 'water-in-bisalt' solution. 

The solution widens the electrochemical stability window of the electrolyte and enables graphite as a cathode material in a practical aqueous system— something previously considered impossible. This helps stabilise the electrolyte at high voltages, allowing the graphite to electrochemically oxidise before the aqueous electrolyte.

The battery showed promising performance during testing. At approximately 2.3 to 2.5 volts, it achieved one of the highest operating potentials of any aqueous battery.

In partnership with colleagues from Argonne National Laboratory, US and the MEET Battery Research Center at the University of Münster in Germany, Pérez formulated a new type of cell chemistry for dual-ion batteries (DIB). The new DIB chemistry uses a zinc anode and a natural graphite cathode in an aqueous electrolyte.

Pérez is building on prior research conducted by Kang Xu from the United States Army Research Laboratory and Chunsheng Wang from the University of Maryland, who first developed these highly concentrated aqueous electrolytes in 2015.

Safer and more sustainable batteries

Cathodes made of highly abundant carbon-based materials, like natural graphite, are less costly and more sustainable than environmentally harmful, scarce, and expensive metals, like nickel and cobalt, which are regularly used in lithium-ion batteries. Using an aqueous electrolyte also makes DIBs safer as they are non-flammable compared to commercial lithium-ion batteries, which exclusively use non-aqueous electrolytes.

In DIBs, both the positive cathode and negative electrode can be made of low-cost carbon-based materials like graphite. This makes DIBs a particularly promising solution to support the widespread adoption of renewable energy sources, like wind and solar for the power grid.

Pérez said: “If we can achieve a high enough voltage for the battery, even if performance is not on par with lithium-ion batteries, we can make dual-ion batteries bigger and make them a suitable candidate for grid energy storage applications. Though you may not be able to use it to power your phone, your local utility can use it to store energy for your home, stabilise the grid, and increase reliability.”

Picture: Ismael Rodríguez Pérez formulated a new type of cell chemistry for dual-ion batteries called graphite||zinc metal aqueous dual ion battery (photo by Andrea Starr | Pacific Northwest National Laboratory)

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Promising research paves way for sodium-ion battery breakthrough

Wed, 06/03/2020 - 14:42 -- paul Crompton

Researchers at Washington State University (WSU) and Pacific Northwest National Laboratory (PNNL) have created a sodium-ion technology they say works as well as a lithium-ion battery.

The team reported their sodium-ion battery is able to deliver a capacity similar to some lithium-ion batteries and keep more than 80% of its charge after 1,000 cycles. 

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Canadian firm in vanadium R&D deal with US lab

Mon, 02/05/2018 - 12:06 -- John Shepherd
Canadian firm in vanadium R&D deal with US lab

Canadian junior mining firm Golden Share Resources Corporation has signed an agreement worth an estimated $906 million with a US government laboratory for R&D into novel vanadium based solid-state battery technologies.

Golden Share said it had signed the deal with Battelle Memorial Institute, which runs the Pacific Northwest National Laboratory (PNNL) for the US Department of Energy.

 

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PNNL leads the charge for better EV batteries

Fri, 08/05/2016 - 15:29 -- Vic
Washington State flag

One of the United States Department of Energy’s national laboratories has been selected to lead research into designing an improved electric car battery.

The Pacific Northwest National Laboratory in Richland, Washington is to guide a $50 million project over the next five years to come up with a smaller, lighter and cheaper battery for electric cars.

The aim of the Battery500 consortium is to create a battery pack with specific energy of 500KWh, bigger than current electric car battery level of 170-200KWh.

The battery pack could also be used to provide better rechargeable batteries for mobile phones and laptops and energy storage before it is needed for the grid.

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