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Chitin & the Electrolytes

The above title is designed to attract curiosity. Yes, it could be the name of a band, but it isn’t. Instead, it involves a proposal to take a potential recycling challenge and to turn it into an electrolyte for use in electric vehicles and integrated battery systems, equivalent to the Tesla powerwall.

Chitin is found in fungi, insects and crustaceans, such as crabs, shrimps and lobsters. It is a polysaccharide = sugar, that makes shells hard and tough. However, because large quantities of crustacean chitin is discarded as food waste, its use has been researched in a variety of applications. In biomedical engineering, for example, it is used as a wound dressing, or as an anti-inflammatory treatment.

By adding acetic acid = vinegar, and processing it chemically (deacetylation), chitin can be synthesized into a gel membrane that can be used as a battery electrolyte = the liquid/ paste/ gel inside a battery that conducts electric current, using ions = positively and negatively charged particles that migrate towards the negative (cathode) and positive (anode) terminals, respectively, allowing it to store energy. This transformation is shown in the illustration below.

The formation of chitosan from chitan using acetic acid. Source: Vicente Neto

When this electrolyte is combined with zinc, it can create a cheap, non-flammable and renewable battery. After 1 000 cycles, the battery is still 99.7% energy efficient. This contrasts with Li-ion batteries, where such a large number of battery cycles can significantly degrade the battery. This is a rare battery characteristic, allowing these batteries to operate at high current density.

Another advantage of a chitin based battery, is that microbial degradation in soil can break down the battery in about five months, leaving zinc behind as a recyclable product.

Notes:

A University of Maryland press release, provides source information about the chemical process for anyone wanting to investigate this topic further.

Report Summary: Rechargeable aqueous Zn-metal battery is promising for grid energy storage needs, but its application is limited by issues such as Zn dendrite formation. In this work, we demonstrate a Zn-coordinated chitosan (chitosan-Zn) electrolyte for high-performance Zn-metal batteries. The chitosan-Zn electrolyte exhibits high mechanical strength, Zn2+ conductivity, and water bonding capability, which enable a desirable Zn-deposition morphology of parallel hexagonal Zn platelets. Using the chitosan-Zn electrolyte, the Zn anode shows exceptional cycling stability and rate performance, with a high Coulombic efficiency of 99.7% and >1,000 cycles at 50 mA cm−2. The full batteries show excellent high-rate performance (up to 20C, 40 mA cm−2) and long-term cycling stability (>400 cycles at 2C). Furthermore, the chitosan-Zn electrolyte is non-flammable and biodegradable, making the proposed Zn-metal battery appealing in terms of safety and sustainability, demonstrating the promise of sustainable biomaterials for green and efficient energy-storage systems.

While originally written 2022-09, publication of this post has been delayed to coincide with the Sharm el-Sheikh Climate Change Conference (COP27) held 2022-11-06 to 18. Politicians love such conferences, using them to receive undeserved publicity for making big promises, that they have no intention on keeping.

Because climate change is real, my hope is that people will:

  1. Use the coming year to find ways to reduce their carbon footprint.
  2. Hold their politicians accountable.

It is also hoped that some, select few people will find this battery concept so interesting that they will use some of their free time to develop an open-source battery. Should one be developed, I am interested in purchasing a 50 kWh battery system, to provide backup when the grid decides to go offline. I would also appreciate being kept informed of developments.

With this weblog post (#451) published, I have 52 posts scheduled, and most of those have been written! In addition there are 71 weblog posts, in draft format, that remain unscheduled. To ease that situation, weblog posts will be published twice a week, on Saturday and Sunday, until the end of 2022. This will add seven posts to the publication schedule. Some of these deal with the 2022 United Nations Climate Change Conference (Cop27), currently being held at Sharm el-Sheikh, Egypt.

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Disruptive Technology: Micro-batteries

Christine Hallquist, CEO Cross Border Power.

World citizens intent on sustainability should rejoice that Vermont citizens were too dumb to elect Christine Hallquist as their governor. Allegedly, they were more concerned about a tax increase on fossil fuels, than they were about entering the 21st century. This means that Christine can use her insights and other talents to help North Americans transition away from fossil fuels to clean electrical energy solutions.

Soon after she lost the election she wrote a white paper on a North-American solution to climate change, which has a lot to do with sustainable electrical energy. Wind and hydro are part of the equation, but so are batteries. Now, she emerges as CEO of Quebec registered, Cross Border Power. Its strategy is closely aligned with that of Bothell, Washington startup XNRGI.

XNRGI (exponential energy) exuberantly tells us that it “has developed the first-ever porous silicon chip based Lithium Metal rechargeable battery technology. XNRGI’s 15 patented technologies and 12 pending patents, were developed over a 15-year period with more than $80-million of investment from Intel, Motorola, Energizer, the United States Navy, Argonne National Laboratory / US DOE Department of Energy grant for advance manufacturing and Novellus Systems, among others. XNRGI’s technologies enable scalable, high-volume manufacturing at the industry’s lowest cost, by using existing semiconductor wafer manufacturing and contract assembly which have been perfected in Silicon Valley over the past 20 years. This combination of original technologies and proven manufacturing processes provides XNRGI with an unprecedented manufacturing scale and at a low cost with minimal capex.”

XNRGI has developed a new battery technology that prints micro-batteries onto silicon wafers. There are 36 million of these machined onto a 300 mm silicon wafer, which is referred to as being 12-inches in diameter.

These batteries can scale from ultra-small batteries for medical implants to large-scale grid storage and initially promises four times the energy density of lithium-ion batteries for half the price. It claims to completely eliminates the problem of dendrite formation which, if true, would make it a massively disruptive invention. Dendrites are responsible for most fires in lithium based batteries.

Porous silicon gives about 70 times the surface area compared to a traditional lithium battery, with millions of cells in a wafer. The batteries are 100% recyclable. At the end of the product life, the wafers are returned, then cleaned to reclaim the lithium and other materials. Then can then be reused.

XNRGI has worked with partners in an early adapter program to test out 600 working samples in a variety of areas. These include: electric vehicles with 3 – 6 times the energy density currently found, while being 2 – 3 times lighter, and at a considerably lower cost; consumer electronics, providing 1 600 Wh/liter; internet of things applications with micron scale power with low discharge rates.

Grid scale storage for intermittent renewables like Solar/ Wind and backup power is another focus area.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 with 40 racks, will offer 4 megawatts (MW) of battery storage capacity in contrast to a comparaAble set of rack-storage lithium ion batteries which would typically only yield 1 MW.

Electrical grid stabilization, is probably the one area in electrical engineering where battery density is irrelevant. Of course, everyone appreciates a price reduction, and this means that a 4 MW 40 foot container will cost twice the price of a 1 MW unit.

A 1 MW 40 foot container-based energy storage system typically includes two 500-kW power conditioning systems (PCSs) in parallel, lithium-ion battery sets with capacity equivalent to 450 kWh, a controller, a data logger, air conditioning, and an automatic fire extinguisher. When this is scaled to 4 MW, some of the details remain unknown, including the number and size of the PCSs. The total capacity should increase to 1.8 MWh.

What is missing from any documentation I have found, is any mention of these batteries in aviation. Because of its importance, this will be the subject of an upcoming weblog post.

Hype

The difficulty with hype, is knowing what technology has a basis in fact, and what is simply wishful thinking. Much hype is related to batteries specifically developed for electric vehicles. Despite chemical engineering studies, including physical chemistry, I lack sufficient insight to judge the veracity of any of these claims. One needs to be a specialist, with detailed knowedge and experience.

The first storage device that raised issues was one under development by EEStor of Cedar Park, Texas. It claimed to have developed a solid state polymer capacitor for electricity storage, that “stores more energy than lithium-ion batteries at a lower cost than lead-acid batteries.” Despite patents, many experts expressed skepticism.

The rise and fall of Envia is another example. This battery startup secured a contract with GM to supply its cathodes, made from nickel, manganese, and cobalt, to power GM’s Volt. Everything looked great until Envia’s cathodes failed to perform as claimed. Details about this can be found in an article by Steve LeVine in Quartz. Later, LeVine wrote The Powerhouse (2015), which more generally discusses the geopolitics of advanced batteries.

Phinergy, as Israeli company, has promoted an aluminum air battery, where one electrode is an aluminum plate, and the other is an oxygen and a water electrolyte. When the oxygen interacts with the plate, it produces energy. The good news is that these batteries could have 40 times the capacity of lithium ion batteries. The bad news is that the aluminum degrades over time. Current only flows one way, from the anode to the cathode, which prevents them from being recharged. This means that the batteries have to be swapped out and recycled after running down.

Fisker Inc. claims it is on the verge of a solid-state battery breakthrough that will give EVs extended range and a relatively short charging period. In contrast to conventional lithium-ion batteries that offer significant resistance when charging or discharging, which creates heat. Solid-state batteries have low resistance, so they don’t overheat, which allows for fast recharging. But the negative side is their limited surface area means they have a low electrode-current density, which limits power. Existing solid-state batteries can’t generate enough power, work well in low temperatures, or be manufactured at scale.

Fisker’s solution is to create a 3D solid-state battery, they call a bolt battery, that is thicker, and with 25 times the surface that a thin-film battery. This allows it to produce sufficient power to move a vehicle. It claims to produce 2.5 times the energy density of lithium-ion batteries can, at a third of the cost. Despite the hype, Fisher will not be providing solid state batteries on its EMotion luxury sport vehicle, claimed to be available from mid-2020. Rather, it will come with proprietary battery modules from LG Chem.

Desertec

This is not the first time I have announced disruptive energy technology. I have been a keen advocate of Desertec solar-thermal power, where I had hoped that electricity generated in North Africa could be used to power Europe (as well as North Africa, the Middle East and elsewhere) with copious quantities of sustainable energy. Bi-products included desalinated potable water (not alw)ays appreciated as a benefit, opportunities for growing large quantities of food, and stabilizing soils to prevent climate deterioration. A White Book has been written on it. It was, and still is my hope, that the introduction of this system would result in more sustainable, and democratic societies, in North Africa, without reliance on fossil fuels.

Readers eager to find weblog posts on Desertec will be disappointed. During the period when I was most interested in this technology (2004 – 2008) I did not have a weblog. Instead, material was presented in the form of lectures and activities in science class, typically for grade 11 students.