Image of Christine Hallquist
Photo: Denial Documentary
Christine Hallquist of Cross Border Power plans to commercialize a porous silicon battery design developed by Washington-based company XNRGI.
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A new Canadian company with roots in Vermont has emerged from stealth mode and has ambitious plans to roll out a new grid-scale battery in the year ahead. The longshot storage technology, targeted at utilities, offers four times the energy density and four times the lifetime of lithium-ion batteries, the company says, and will be available for half the price.

 

The new company’s CEO, a former Democratic nominee for governor of Vermont, founded Cross Border Power in the wake of her electoral loss last November. Within days after the election, she was at her computer and writing a thesis (since posted on her campaign website) that she boldly calls “[The] North American Solution to Climate Change.”

 

One of Christine Hallquist’s planks as gubernatorial candidate was to set the Green Mountain state on a path to obtaining 90 percent of its energy from renewable sources by 2050. In the final weeks of the election, the Republican Governors Association attacked Hallquist’s campaign by claiming her vision would raise taxes on Vermonters and hike gasoline prices at the pump.

 

Today, she might agree that economics may indeed shape the future of renewable energy—but through low prices, not high ones. “I think we’re at the point, especially with our batteries, that renewables are going to be cheaper than any of the fossil fuels,” she says.

 

Before she ran for governor, Hallquist was CEO of the Vermont Electric Cooperative where she experienced firsthand the difficulties of transitioning to renewable energy without viable grid-scale storage.

 

Through her new venture, she’s now trying to provide a solution to wind and solar energy’s intermittency. That opportunity emerged after she published her “Solution” paper online, in which she wrote: “Battery storage is the holy grail for extensive deployment of renewables.”

 

A group of Canadian investors and venture capitalists, having followed Hallquist’s gubernatorial run and read her climate change “Solution” position paper, contacted her about a battery technology that was still in stealth mode. The investors, who Hallquist says are themselves still keeping out of the public spotlight, began as a Canadian assortment of venture capitalists and have since expanded to include a number of American financiers as well.

 

The battery they’re touting is made by the Bothell, Wash.-based company XNRGI. According to its website, an XNRGI cell uses existing silicon semiconductor manufacturing technology to engineer a “porous” silicon battery. “Think of a traditional silicon wafer that we use for all of our electronics today,” Hallquist says. “They etch a 20 x 20 micron honeycomb into that silicon to make a porous silicon. They use the same wafer for the anode and the cathode.”

 

The idea behind the XNRGI battery is an unconventional one, depicted in a two-minute explainer video and five-page white paper [PDF] from the company. The etched silicon wafers, which are later coated with lithium and other metals to form anodes and cathodes, contain forests of micro-sized batteries on each silicon wafer. Think of each “micro-battery” as an elongated hollow box with a 20 x 20 micron footprint. The cathode and anode are the top and bottom half of that hollow box, separated by some distance from each other. No individual micro-battery, Hallquist says, contains enough charge current to form substantial dendrites or other structures that could arc the positive and negative ends of the battery.

 

And each 12-inch silicon wafer consists of some 36 million of these vertical “micro-batteries” machined into the wafer’s surface. Which, as the explainer video argues, decreases the charge time of the macro-battery (made up of many micro-batteries) as well as the manufacturing cost of the technology, as it’s based on already scaled-up silicon fabrication processes used in computer chip manufacturing today.

 

Hallquist says the company’s technology is covered by 15 patents (and 12 pending patents) and supported with more than US $80 million investment from private and public sources.

 

According to the company’s white paper, XNRGI has “has already built more than 600 working samples (8 billion micro-batteries) for a wide range of clients.”

 

It was the group’s work at the individual battery cell level, Hallquist says, that convinced her that XNRGI’s battery was “ready for commercialization.” So Hallquist secured exclusive rights to sell and distribute the XNRGI battery technology to the North American power market. (These are rights that her company, Cross Border Power, which is based in Quebec, only finalized last week.)

 

 

Hallquist says the battery banks that Cross Border Power plans to sell to utility companies as soon as next year will be installed in standard computer server racks. One shipping container worth of those racks (totaling 40 racks in all) will offer 4 megawatt-hours of battery storage capacity, she says. Contrast this, she adds, to a comparable set of rack-storage lithium ion batteries which would typically only yield 1 megawatt-hour of storage in a shipping container.

 

Hallquist adds, however, that packing traditional lithium ion cells into a metal shipping container that’s exposed to summer heat can be dangerous, given the problem of thermal runaway. The XNRGI battery, Hallquist says, will not have that problem. “When you use porous silicon, you get about 70 times the surface area compared to a traditional lithium battery… [and] there’s millions of cells in a wafer. It completely eliminates the problem of dendrite formation.” And with no dendrites, the risk of thermal runaway disappears.

 

The last benefit, she says, is the XNRGI cells’ recyclability. “At the end of the life of this product, you bring the wafers back in, you clean the wafer off, you reclaim the lithium and other materials. And it’s essentially brand new. So we’re 100 percent recyclable.”

 

Yet, Hallquist says providing battery storage at utility scale is still not a simple problem. One 4-megawatt shipping container pales in comparison to the 222 gigawatt (GW) capacity that renewables represented in the United States in 2018. And, of course, the amount of renewable energy in the electrical grid is only going up.

 

“It’s a tremendous engineering challenge,” Hallquist says of the battery storage problem. “But I would posit that, of course, we can do it.”

This post was updated on 19 July.