The scientists used an organic redox polymer based on phenothiazine as a new electrode material that exhibits a surprisingly high storage capacity that surpasses that of graphite electrodes.

Aluminum-ion batteries have long been attractive as an alternative to conventional lithium-ion batteries. This is mainly because aluminum, a common and widely available material, is recyclable and inexpensive compared to lithium, a rare and expensive raw material. However, the main drawback of aluminum-ion batteries is their insufficient storage capacity. The challenge is the lack of appropriate host electrode materials that can enable the reversible insertion of complex aluminum ions.

(Image: Author.)

The storage capacity known as specific capacity (mAh/g) is the amount of electric charge (mAh) delivered by the electrode per gram of material. Since the specific capacity is mainly determined by electrode material, the researchers have been experimenting with various positive electrode materials to increase an aluminum-ion battery’s electric charge. Their work and results were published in the journal Energy & Environmental Science.

Electrode material that inserts complex aluminum anions

To improve the electrode material for Al-ion batteries, the scientists’ approach was to find a more effective mechanism to insert complex aluminum anions in the electrode with high reversibility. Generally, p-type organic compounds can be reversibly oxidized at high potentials, storing and releasing anions at fast C rates. The researchers focused on developing new organic redox-active materials that exhibit high performance and reversible properties. For the first time, they successfully demonstrated a reversible two-electron redox process for a phenothiazine-based electrode material.

As a positive electrode material, the researchers used an organic redox polymer capable of reversibly inserting two anions (AlCl₄), providing higher specific capacity compared to graphite. These electrodes are marked as X-PVMPT, which means cross-linked poly(3-vinyl-N-methylphenothiazine). The tested battery uses a liquid EMIm chloroaluminate electrolyte, which is considered the best electrolyte for Al-ion batteries when comparing the cost, electrochemical stability and temperatures that maintain the electrolyte in a liquid state.

Illustration of the battery redox process. The electrode material is oxidized and aluminate anions are deposited. (Image: University of Freiburg / Birgit Esser.)

The obtained experimental specific capacities were up to 167 mAh/g, which is higher than the graphite electrode (the graphite-specific discharge capacity is limited to 120 mAh/g). The higher specific capacity of an electrode indicates that more aluminum ions can bind to the electrode. Practically, this provides a larger battery storage capacity, which would mean, for example, longer driving ranges for electric vehicles.

Additionally, the new electrode provides superior cyclability at fast C rates, a measure of how fast the battery is charged or discharged. For example, 1C means full battery charging/discharging in one hour, 0.5C in 2 hours, and 10C in 6 minutes. A higher C rate means more stress on the battery, and dangerous dendrites can be formed on the electrode, shortening the lifespan and increasing the possibility of cell failure. The battery’s ability to recover capacity after a higher C rate provides the possibility of fast charging and high discharging current in demanding applications.

The experimental results showed that the battery holds 88% of its capacity even after 5,000 cycles at a 10C rate. The tests were performed at an extremely high 100C rate where the battery remained at 64 mAh/g. At lower C rates, the battery’s original capacity remained unchanged.

X-PVMPT-based electrodes insert negative ions (anions AlCl₄ or Al₂Cl₇) at average charge potentials of 0.81 and 1.65 V versus positive aluminum ions. As the difference between the electrode potentials is larger, the electromotive force (EMF), or cell voltage, is higher. Thus, the cell is capable of producing a higher amount of energy. Cell voltage is determined by the compatibility of all battery parts—the anode, cathode and electrolyte. The experiment also showed that the plateau at a higher potential (average 1.48 V) favorably contributes to a higher amount of the specific capacity than the plateau at a lower potential (average 0.74 V), proving that a larger amount of charge can be stored in the new electrodes at the higher potential.

“With its high discharge voltage and specific capacity, as well as its excellent capacity retention at fast C rates, the electrode material represents a major advance in the development of rechargeable aluminum batteries and thus of advanced and affordable energy storage solutions,” said researcher Birgit Esser in a press release issued by the University of Freiburg.

This research represents the first insight into the aluminum-ion battery performance that could be achieved using the phenothiazine-based electrode with a reversible two-electron redox process. With its high discharge voltage and specific capacity, as well as its excellent ability to retain capacity at fast C-rates, this research could enable the development of advanced and affordable Al-ion batteries. The results could also initiate further research and improvements on positive electrode materials based on organic redox polymers.

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There are numerous research projects focused on solving these challenges, but the most promising one is increasing the battery voltage. Today’s EV batteries are commonly 400-volt systems, but EV manufacturers have already begun redesigning their vehicles to shift to 800-volt architectures.

Higher battery voltage means more energy and higher charging power, plus increased efficiency, better performance and weight savings for EV components such as motors and inverters. But high voltages come with new challenges as well. Here’s a look at why the EV industry is so keen to move to higher voltages—and how engineers are making it happen.

What it means to have a 400-volt or 800-volt EV architecture

The architecture of an EV is a complex system involving batteries, motors, sensors, electronic controls, auxiliary equipment, wiring and other components. The battery voltage, whether 400 volts or 800 volts, affects all of them.

An 800-volt system architecture requires redesigning many components in an EV. (Image: Porsche.)

These values are not as fixed as their name suggests. For example, a battery voltage range of 300 – 500 volts is referred to as a 400-volt architecture, and a 600 – 900 volt range is considered an 800-volt architecture. Shifting to an 800-volt architecture is not a matter of simply connecting batteries to get a voltage of 800 volts; this operating voltage is a key parameter for designing all other high-voltage devices in the car.

Why EV manufacturers want to shift to 800 volts

Higher battery voltages mean increased EV efficiency, improved performance and better charging. For drivers, that means faster charging and less energy consumption.

The main parameter for charging speed is charger output power, which depends on voltage and current. Increasing the charging current would lead to more heat and energy loss, so increasing the voltage is a better way to increase power and get faster charging. With double the voltage and equal current, an EV charger could deliver almost twice the energy to EVs. Of course, the chargers and EV’s converters have to be redesigned to be able to carry significantly higher power.

The 800-volt architecture also reduces energy consumption. If a battery outputs the same power as its voltage increases, that means its current must decrease. Since heating and power losses are proportional to the square of the current, heat loss goes down as voltage goes up. Lower current also has a positive effect on battery aging, thereby extending the battery life.

Challenges of the 800-volt EV architecture

The 800-volt EV architecture has unquestionable advantages, but there are still challenges that must be overcome to smoothly integrate the technology in the market.

Charging infrastructure is the first issue. Charging speed depends on charging stations, and most are built to provide power for 400-volt EVs. To take full advantage of faster charging capabilities, 800-volt EVs will require more powerful charging stations.

Another issue is in EV design. The 800-volt architecture requires redesigning the circuits and components to ensure appropriate insulation, fail-safe systems and the right test procedures to prove the reliability of components in a high-voltage environment. The testing procedures must cover worst-case scenarios up to five times higher than the operating voltage of 800 volts.

The equipment costs tend to be higher for 800-volt EVs as well. For example, they tend to use pricier silicon carbide (SiC) switching components in power converters. SiC enables increased switching frequency with very low energy losses (2%) when compared to traditional silicon-based converters (5 – 6%). However, because of the lower current in 800-volt EVs, the wires and links can be thicker and cooling requirements are lower.

There are also safety concerns. Higher voltage systems need more physical space to avoid problems like overvoltage and arcing. Capacitors, for instance, require a minimum creepage distance between polarities to avoid arcing. As the voltage is higher, the required distance is longer—meaning bigger capacitors. This is very unfavorable for EV manufacturers, who want to make everything smaller and lighter to increase efficiency.

Different solutions for the 800-volt architecture

EV manufacturers have analyzed various approaches to overcome the challenges of 800-volt architectures. There are three promising approaches.

The first approach is to make the entire EV’s high-voltage system operate on 800 volts, eliminating the need for voltage conversion between components. This approach enables faster charging and better efficiency. However, it requires more EV redesign and higher costs.

The second approach is to have only some essential devices (like the battery pack and drive motor) on 800 volts, with the rest of the system remaining at 400 volts. The need for voltage conversion between 800- and 400-volt devices increases the cost and design complexity, and also adds conversion power losses. However, this solution requires less EV redesign and lower costs for the 400 V system, while still enabling faster charging.

The third approach is a hybrid solution that involves a battery system capable of switching between 800 volts when charging and 400 volts when discharging. Other high-voltage devices remain at 400 volts. This simple and low-cost solution enables faster charging, though discharging at 400 volts means that a reduction in energy consumption will not be achieved.

We will probably see all three approaches as EV manufacturers switch from 400 volts to 800 volts. As testing procedures develop and prices fall for 800-volt components, we can expect a full transition to the high voltage architecture. For heavy duty EVs that require high power, we may even see architectures beyond 800 volts.

Why Tesla is holding out on 800-volt EVs

The transition to 800-volt EVs is already well underway. Automakers Porsche, Hyundai, Genesis, Kia and Audi already offer EVs with 800-volt battery systems. Volvo, Polestar and Lotus have also committed to 800-volt architectures. Hitachi Automotive Systems is starting mass production of its 800-volt battery system.

The Porsche Taycan was the first production EV with a system voltage of 800 volts, according to Porsche. (Image: Porsche.)

Interestingly, EV pioneer Tesla has not committed to shifting to the 800-volt architecture. CEO Elon Musk has questioned the value of the transition, suggesting it’s not worth the cost of redesign just yet—at least for the company’s smaller vehicles like the Tesla Model Y and Model 3. In the long term, though, he believes that an 800-volt architecture would make sense for a high volume of vehicles.

It may take some time, but one way or another, the EV industry is shifting into high voltage.

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Detailed in a January 2023 paper in Advanced Energy Materials, the novel battery concept has already been patented, paving the way for an appearance in the real industry sector. However, oxygen-ion technology will probably not beat the current kingpin, lithium-ion, in all applications. It does not have as high an energy density as Li-ion batteries, but it does have numerous advantages, especially for one important application: large energy storage systems (ESSs) such as renewable energy sources, power grids, microgrids and more.

The ceramic advantage

Ceramic is the key to the new oxygen-ion batteries. The Vienna University of Technology researchers developed ceramic materials that can absorb and release doubly negatively charged oxygen ions, so the oxygen ions can migrate from one to another ceramic material. Ceramic materials are the key components in OIBs and provide ionic conductivity, stability and durability for the battery.

Prototype of an oxygen-ion battery. (Image: Vienna University of Technology.)

The battery prototype uses lanthanum, which is not widely available and is still expensive. However, lanthanum can be easily replaced with cheaper and more widely available materials, and the researchers are already working on doing so. Better yet, the expensive elements cobalt and nickel, common in today’s lithium-ion batteries, are not used at all.

“In this respect, the use of ceramic materials is a great advantage because they can be adapted very well. You can replace certain elements that are difficult to obtain with others relatively easily,” said researcher Tobias Huber in a Vienna University of Technology news release.

How oxygen-ion batteries work

Oxygen-ion batteries work similarly to lithium-ion batteries. Like Li-ion batteries, where lithium is incorporated in electrodes, neutral oxygen can be incorporated in OIBs by annihilating oxygen vacancies and creating electron holes. 

The electrodes of OIBs are composed of a ceramic material with a high oxygen affinity, such as perovskite-type oxides. Mixed conducting oxide electrodes can change stoichiometry (depending on the oxygen chemical potential), and thus absorb and release oxygen ions during the battery charging and discharging process. For this purpose, MIEC oxides (mixed ionic electronic conducting perovskite-type oxides) are used to create thin film electrodes with blocked oxygen surface exchange. The researchers investigated different variations of electrodes, such as LSM, LSCF and BSCF. These have the ability to conduct both electrons and ions, and oxygen can be incorporated or evolve on the entire electrode surface.

The oxygen-ion battery’s solid state electrolyte uses a ceramic material with high oxygen ion conductivity, enabling the migration of oxygen ions between the cathode and anode while preventing electronic conduction. The researchers used yttria-stabilized zirconia (YSZ) single-crystal electrolytes. The zirconia layer is constructed for oxygen blocking.

The prototype battery demonstrated good cycling performance, with less than 1% of the charge being lost per cycle. The tested cells had a 0.6V cell voltage, so future optimization of OIBs could see a higher cell voltage, perhaps using different electrode materials. 

OIB benefits and future improvements

Ceramic material is a good step away from the rare, non-environmentally friendly materials used in most batteries today. It is also not flammable, which solves the biggest issue of Li-ion batteries: fires. Solid-state ceramic electrolytes pose no risk for leakage or thermal runaway and enable more compact and flexible battery configurations and designs.

The most prominent advantage of OIB is its long life span. Most of the available battery technologies lose their capacity after many charging cycles. When oxygen is lost due to side effects, OIB can be regenerated with ambient oxygen.

However, there are still challenges to overcome before OIBs will work in the real world.

OIB batteries do not have ideal properties, and they will probably not be the best choice for all applications. Their energy density is significantly lower than Li-ion batteries, which deters wide use in small electronic devices such as smartphones, or in electric vehicles (EVs), especially as their operating temperature is between 200 and 400 °C. There is room to improve oxygen-ion conductivity by developing high-performance ceramic electrolytes. However, high-performance ceramic materials should have reasonable prices that can be achieved by optimizing material synthesis processes and reducing production costs.

Nonetheless, OIBs are still very interesting in ESS applications such as storing solar and wind energy, where space and temperature do not play a key role. OIBs can provide long service life and could be produced in large quantities due to their widely available materials. This novel battery may also prove useful for applications requiring elevated operating temperatures, for which common cation-based cells are not applicable so far.

The post Meet Oxygen-ion, the New Battery That Regenerates Itself appeared first on Engineering.com.

As such, there is a need to develop sustainable recycling solutions to manage the growing heap of used batteries and minimize their environmental impact. As a potential solution, some researchers are looking under the sea to find environmentally friendly materials for greener batteries—and they’re coming up with treasure.

Crabby batteries

In September 2022, researchers from the University of Maryland developed a zinc battery with a biodegradable battery electrolyte using chitosan, a material derived from crab shells. The promising results were published in Cell Press by Wu et al.

Today’s battery electrolytes, which transfer ions back and forth between battery electrodes, typically comprise flammable or corrosive chemicals. In contrast, the crab-based electrolyte material is non-toxic, non-flammable, and a natural material that’s readily available (just watch out for pincers).

Chitosan, a biopolymer derived from crustacean shells, is a biodegradable material for battery electrolytes. (Source: Wu et al.)

Chitosan is a biopolymer derived from chitin, which is extracted from the exoskeletons of crustaceans like crabs and shrimp. Microbes can decompose chitosan within five months, leaving behind the recyclable metal zinc rather than lead or lithium.

And it’s not just good for the environment. The researchers found that the chitosan electrolyte makes a pretty good battery, too, with high ionic conductivity and good thermal stability. The researchers’ chitosan-based zinc batteries demonstrated good performance, high energy density and a long life cycle.

Although this biodegradable technology is still in the experimentation phase, it has the potential to replace conventional battery electrolytes to enable greener and more sustainable energy storage.

Seaweed could save sodium-ion batteries

Researchers from the University of Bristol are on the way to solving the biggest issue of sodium-ion batteries, one of the most promising alternatives to lithium-ion batteries. Though sodium-ion batteries have a high energy density and low cost, they suffer from drawbacks including a limited life cycle due to uncontrolled sodium dendrite growth.

Dendrites can penetrate through the battery separator and contact the battery’s cathode, causing an internal short circuit. The Bristol researchers looked for a way to improve the separator—and perhaps they were eating sushi when the inspiration struck to use seaweed.

Traditional lithium-ion batteries use polypropylene and polycarbonate separators, but these materials take thousands of years to degrade. The Bristol researchers developed a new separator using cellulose nanomaterials derived from brown seaweed. The seaweed-based separator not only enables a more efficient sodium-ion battery, but a more environmentally friendly battery as well.

The separator is an important part of the battery. It divides electrodes, preventing contact between cathode and anode, and enables free transmission of charge between them. The seaweed-based cellulose nanomaterials make the separator strong enough to resist dendrite penetration, one of the issues preventing widespread adoption of sodium-ion batteries.

Cellulose nanomaterials can be an effective alternative to costly and non-biodegradable carbon nanotubes. The seaweed-based material is widely available, low-cost and environmentally friendly since it’s biodegradable.

Battery separators made from seaweed have the additional advantages of being flexible, easily adjustable and thermally stable. Good mechanical properties are crucial for battery separators to prevent deformation under high temperatures. In case of thermal runaway, this prevents a short circuit, ensuring stable and safe battery operation under a wide operating temperature range.

Demonstrating the mechanical flexibility of the seaweed-based separator. (Source: Wang et al.)

In their experiments, the University of Bristol researchers found the seaweed separator resistive to penetration by dendrites from the sodium electrode. Their battery made with the separator showed high operating performance, with a long cycle life of over 1000 cycles (with 0.037 percent capacity fading per cycle). The researchers published their work in September 2022 in Advanced Materials.

The seaweed separator can also be effectively used in other battery types, such as zinc, aluminum, calcium and magnesium metal-based batteries. Given the environmental friendliness and low cost of the material alongside its promising results, this work provides a good base for future, greener batteries.

What other material treasures might the sea hold in store? Whatever it is, battery researchers may have to get a little wet for the next big breakthrough.

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See: How to Give EV Batteries a Second Life

Old EV batteries can be repurposed for many useful applications that have less demanding power requirements than EVs. Many recent projects involving automakers, utilities and energy management companies suggest that this approach may soon become the norm.

A second life off the grid

Second-life battery applications can be grouped into three main categories: off-grid stationary applications, on-grid stationary applications and mobile applications.

Off-grid stationary applications, also known as independent energy storage systems (ESSs), provide power to isolated systems that are not connected to the primary electrical grid. Battery energy storage systems are a prime use case for second-life batteries.

Energy storage systems could be beneficial to many industries. They could replace diesel generators in remote applications and provide flexibility to industrial users with high energy demands. ESSs are convenient in the energy arbitrage business of buying and storing electricity during off-peak periods and selling it during peaks.

Renewable energy sources can also benefit from using second-life batteries for storage, as ESSs can eliminate the intermittence of renewable energy sources such as wind and solar. Residential and commercial customers are a huge market for second-life batteries, as they can replace existing generator systems by storing and selling surplus energy.

It is important to analyze the risks of using second-life EV batteries for ESSs. The majority of EV batteries use lithium ion technology, well-known for its fire risk in the event of improper handling. The higher the required power, the higher the risk. From that point of view, second-life EV batteries may be more viable for small-scale applications.

See: Why Do Good Batteries Go Bad?

Second-life EV batteries for the grid

ESSs can also be effective for on-grid applications, as they provide both technical and economic benefits for electric utilities. With ESSs, utilities can postpone building new power plants and transmission infrastructure, and reduce purchasing energy from third parties when demand exceeds capacity.

See: How Batteries Are Boosting the Power Grid

Second-life batteries are also promising as part of frequency regulation systems for the power grid. It is essential to keep the grid’s voltage, power and frequency stable prevent damaging equipment and infrastructure. In particular, frequency must be kept within strictly defined limits—typically below one percent—as imposed by regulators such as the Federal Energy Regulation Committee (FERC) in the U.S.

Frequency deviation is caused by differences in energy generation and consumption requirements. When the grid frequency drops, protective relays automatically initiate load shedding to restore system frequency.

Power plants usually maintain constant generation to ensure system stability. Generators have high inertia and cannot quickly adapt to a changing grid load, which is a challenge for traditional frequency regulation. This means that the energy needs to be absorbed somewhere when demand is reduced (downward regulation) and when demand increases, the regulation system must provide energy quickly (upward regulation).

Second-life batteries could be used alongside gas turbine generators to provide quick energy to the grid. Though this is a promising application, so far there is scant data on its viability.

EV batteries charging EV batteries

Charging stations are a key factor in EV deployment. More EVs on the street requires more EV infrastructure, and second-life EV batteries are a natural fit for EV charging stations.

Battery-powered EV charging stations do not require a permanent connection to the grid, and can be powered by renewable energy sources such as solar panels. So-called mobile charging stations are designed for simple and quick deployment at any location, which is particularly advantageous for distant or isolated areas. Mobile chargers have the potential to strengthen the existing charging infrastructure system.

Mobile charging stations can be taken a step further. Some companies are developing fully autonomous EV charging robots that can top off a battery tank with no human intervention. EV Safe Charge’s Ziggy charging robot, for example, helps EV drivers find parking spaces and then charges their car.

The Ziggy EV charging robot makes any parking spot an EV charging station. (Source: EV Safe Charge.)

Second-life EV batteries around the world

Many are interested in the promise of second-life batteries, from governments and utilities to investors and manufacturers of batteries and EVs. The latter will be a key player in the second-life battery business, and many EV manufacturers have been considering the concept as a business opportunity and an important step in the circular economy. 

For example, Volvo experimented with second-life EV batteries in a 2021 collaboration with Nordic energy producer Fortum and Swedish energy management solution provider Comsys. The companies used 48 out-of-service EV batteries from Volvo hybrid vehicles for a 250kWh energy storage system at Fortum’s Landafors hydropower plant on the Ljusnan river in Sweden.

“Volvo Cars has big ambitions with regards to the circular economy and we are putting great effort in finding new business models that enable us to maximize battery usage over the course of their entire life cycle. This project is in line with those objectives and will offer us new insight about the batteries’ lifespan and how they can be used outside of our cars,” said Susanne Hägglund, head of Volvo’s car service business, in a Fortum press release.

A second-life battery energy storage system at the Landafors hydropower plant in Sweden. (Source: Fortum.)

In Japan, automaker Nissan is part of a joint venture called 4R Energy that determines the next step for expired EV batteries (the four R’s stand for recycle, refabricate, reuse and resell). The company determines the best secondary application for every battery based on a letter grade—A-grade batteries may be fit for new EVs, B-grade batteries for industrial machinery or energy storage, and C-grade for backup power units, for example. According to Nissan, these batteries have a second-life span of 10 to 15 years.

French automaker Renault has contributed depleted batteries from its Kangoo Z.E. electric vans to a second life in E-STOR frequency response systems, built for grid operators by U.K. firm Connected Energy. Elsewhere in Europe, German automakers BMW and Audi have each also engaged in partnerships to give a second life to their EV batteries.

Though the use cases for second-life batteries are still being proven, their promise is undeniable. Not only do they promote more sustainable design, they provide novel opportunities for automotive companies, grid operators, energy storage providers, EV charging companies, property owners, investors and—most importantly—engineers.

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Second-life batteries present an intriguing business opportunity as well as a chance to increase EV sustainability—but there are a few challenges left to solve.

Second-life batteries are batteries that have reached the end of their primary application life, but still have enough capacity to be used in less demanding applications. Manufacturers usually suggest replacing Li-ion batteries when they reach 70 to 80 percent of the initial rated capacity. This reduced capacity cannot guarantee the required performance and safety for primary applications—like EVs—but the batteries could still be used in many other applications, such as renewable energy storage, EV charging stations, forklifts, and power grid applications for frequency regulation and peak shaving.

Second-life batteries can be a key contributor to increasing the adoption of EVs. They can directly influence affordable charging infrastructure, reduce battery costs and environmental impacts, and contribute to the sustainability of the battery market. They can also offset the price of EVs, of which batteries are the most expensive component (typically around two-thirds of the total EV cost).

In the battery business, the circular economy is key for providing price competitiveness, affordability, environmental accessibility, and sustainability. Disposal of old batteries is environmentally damaging, demanding, and complex as they usually contain harmful metals and toxic chemicals. Still, many batteries are inappropriately discarded in the environment every day, causing immense damage.

New batteries are more efficient and developed to last longer, so their premature disposal is a waste of resources. Instead of discarding these batteries, it is more efficient to give them a second life in form of the repurposing, refurbishment, or recycling.

Battery recycling (recovering the key materials) is standardized and affordable for lead-acid batteries, but recycling Li-ion batteries still has many barriers to overcome. These include a lack of standards, a high price, and high energy demand, as well as challenges with high battery density. Since there are just a few places providing proper recycling technology, many batteries must be transported, causing logistical and safety problems as well as increasing costs. Currently, the cost of recovering materials is comparable to the cost of raw materials.

An Effective Second-life Battery Approach

Rather than recycling worn-out batteries, repurposing them for less demanding applications can increase battery lifetime and revenue for manufacturers. It also helps preserve the environment by buying time for manufacturers to develop effective recycling facilities. When considering the drawbacks of today’s battery recycling technology, reusing batteries looks like the more environmentally-friendly option at the moment.

Besides environmental benefits, battery reuse has business benefits as well. It helps companies to achieve carbon credit requirements. Integrating second-life batteries into the power system can postpone building new power generation plants and make renewable energy systems more accessible.

The second-life battery business includes removing batteries from EVs and integrating them into other applications. The first step of the business strategy is identifying the key customers and the value that can be offered to them.

Residents, companies, and energy producers who want to install renewable energy will consider energy storage systems (ESSs). Second-life batteries can offer lower-cost ESSs.

Utilities can benefit from affordable ESSs through effective frequency control, quick energy reserves, power management, and postponing investment in new infrastructure.  

Companies that manufacture or use batteries have the potential to increase their business with second-life battery services.

In a March 2023 Journal of Energy Chemistry article entitled “Towards a business model for second-life batteries—barriers, opportunities, uncertainties, and technologies,” battery researchers discuss several potential business models for second-life batteries.

The paper highlights three business models: the closed market, the intermediary-based market, and the open market.

The closed market model means that the original equipment manufacturer (OEM) rents the batteries to EV owners. When the batteries reach the end of their life, it is the OEM’s responsibility to recycle them (collecting, testing, classifying, and repurposing). This business model is important for OEMs who want to protect their technology and are not willing to share key battery information outside the company. However, they must be able to implement the whole recycling process.

In the intermediary-based market model, OEMs make agreements with logistics companies who are responsible for the recycling process. They collect spent batteries with or without the cooperation of other companies that develop and distribute ESSs, EV charging stations, etc. The logistics company is the link between the OEM and end-user, meaning OEMs must share the relevant information and data about their technology with the intermediary. This presents a risk for OEMs, who also weaken the chance for future business in this area and potentially damage their brand if their batteries do not provide good performance in secondary applications.

The open market model includes market operators to connect battery customers and sellers through online platforms. The platforms should manage inventory considering the supply and demand of second-life batteries. As intermediaries, market operators earn a percentage of the transaction value. However, the platforms have to be capable of supporting and assisting customers in specifying the batteries and ESS specifications. The open market is probably the most challenging model, as it requires well-developed blockchain technology to protect sellers and buyers, and battery prices are individualized to account for different histories and operating conditions. 

Battery manufacturers are the most suitable candidate for managing second-life battery applications. They know the most about the batteries, their design, how they degrade, the performance of the spent batteries, and for which applications they are most suitable. They also know how to adapt the batteries and optimize performance for a given application. Battery manufacturers will play a key role in defining the standards and regulations for second-life battery applications.

Despite the advantages, reusing batteries has some uncertainties. It is an open question whether the amount of batteries currently in use is sufficient to cover the needs of the secondary application market.

Furthermore, there are no regulations about the required performance of second-life batteries or product warranty conditions for the customer. The business structures are still not clearly defined, such as the testing procedures for reused batteries and the procedures of replacing and transporting the batteries. Since battery prices are decreasing, the price competitiveness of used batteries is questionable as well.

Manufacturers are cautious about this business opportunity, both because their battery data is confidential and for fear that second-life batteries could affect their core business. Direct recycling sounds a more effective option for manufacturers, but it requires expensive and complex infrastructure. Second-life batteries could be a transition phase while recycling facilities are established.  

Although second-life batteries hold a lot of promise, additional studies are needed to define regulations and to provide a clearer picture of profitability and the costs involved in installation, operation, maintenance, and testing. The goal remains to make second-life batteries more economically viable than new batteries.

For more on the applications of second-life batteries, read: EV Batteries Find New Purpose On and Off the Grid.

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But what will be the most dominant battery in the future? Despite their advantages, today’s Li-ion batteries have well-known drawbacks related to safety and material availability, and battery researchers are busily exploring many possible alternatives.

One of the most promising of these is lithium-sulfur (Li-S) batteries, which can store even more energy than today’s Li-ion batteries—but they have one big disadvantage that engineers will need to overcome.

Lithium-sulfur batteries use sulfur as the cathode, compared to the nickel, manganese, and cobalt commonly found in Li-ion cathodes. Unlike those expensive and rare elements, sulfur is plentiful and can be found almost anywhere on Earth.

Even better, Li-S batteries have double the energy density of Li-ion batteries, meaning more power for less weight. And the technology can easily be mass-produced, as the manufacturing process for Li-S is similar to Li-ion batteries and can re-use existing plants. Plus, Li-S requires much less production energy since sulfur only requires 112˚C to melt into crystal form.

So, what’s the catch?

Lithium-sulfur batteries are far from a new idea, with the chemistry first being patented in 1962 by Herbert Danuta and Ulam Juliusz. There’s a good reason they haven’t had commercial success in the years since. Li-S batteries suffer from one major challenge: charging cycles. While lithium-ion batteries can handle up to a few thousand charge cycles, lithium-sulfur batteries can’t even reach half of that.

Li-S batteries have difficulty re-depositing lithium evenly on the anode during recharging. The source of the problem is the internal chemistry of Li-S batteries. During the charging process, Li-S batteries form and accumulate chemical deposits in tree-like structures—dendrites—that spread from the lithium anode. These deposits degrade the anode and electrolyte, shorting the battery lifespan and reducing the power it can deliver. They can even cause internal short circuits and fire given a flammable electrolyte.

Solving this issue has become the focus of many research projects, as it is essential to make Li-S batteries a realistic alternative to Li-ion.

The EU-funded LISA project, which finished at the end of last year, studied different ways to optimize Li-S batteries to be reliable and effective in small electric vehicles. For example, one approach used a laser to integrate tiny layers of ceramic composite on the anode to prevent the formation of dendrites.

Researchers are also working on improving the Li-S electrolyte to minimize the risk of battery fire. Instead of a gel or liquid electrolyte, which is susceptible to fire, they experimented with solid ceramic elements combined with a flexible polymer. LISA researchers also considered a heat-sensitive cut-off material (fuse) inside the battery that could switch off electrical current flow if the temperature increases too quickly.

Researchers are also thinking about removing the need for lithium in Li-S batteries. Instead of lithium, they would use sodium to build sodium-sulfur batteries. This more eco-friendly solution would eliminate a massive supply chain bottleneck.

However, the biggest challenge remains. To integrate Li-S batteries in the transportation market, they’ll need a significantly higher number of cycles. If battery researchers can effectively solve this problem, Li-S batteries could see mass adoption by the end of the decade.

While researchers look to expand the possibilities of Li-S, there are already several manufacturers that can deliver Li-S batteries. The batteries are used in certain applications where weight and a long running time with a single charge are crucial, such as drones or satellites.

In 2020, LG Energy installed a Li-S battery in a High-Altitude Long Endurance (HALE) solar-powered Unmanned Aerial Vehicle (UAV) developed by the Korea Aerospace Research Institute. It had a successful 13-hour test flight at the highest altitude possible in the stratosphere, subject to a temperature of -70˚C and a pressure just four percent of ground level.

A German battery startup called Theion is working to bring Li-S batteries to electric vehicles (Theion is Greek for sulfur). The company’s website says it expects to have samples of its Li-S technology for automotive customers as early as 2024. 

Whatever the timeline, it seems that sulfur could solve many of our energy issues—if engineers can solve sulfur’s issues first. 

The post Lithium-Sulfur Batteries Could Be The Future of Energy Storage appeared first on Engineering.com.

A small part of that damage came in an unsuspected way: the storm proved disastrous to several electric vehicles (EVs), whose lithium-ion batteries ignited after prolonged exposure to saltwater. In Florida’s Collier County, the North Collier Fire and Rescue Department responded to at least six EV fires since Hurricane Ian and knew of others across southwest Florida, according to its October 11 Facebook post.

A Tesla Model S destroyed by a battery fire caused by saltwater flooding. (Source: North Collier Fire Control and Rescue via Facebook.)

“There’s a ton of EVs disabled from Ian,” tweeted Florida’s Fire Marshal Jimmy Patronis on October 6. “As those batteries corrode, fires start. That’s a new challenge that our firefighters haven’t faced before. At least on this kind of scale.”

What causes this issue, and what can EV makers do about it?

Not Just a Normal Fire

The physics of the hurricane problem are easy to understand. EV batteries have a lot of stored energy. Seawater contains highly conductive salt. Together, those facts set the stage for an explosive short circuit.

But it’s worse than that: the heat and gasses generated in Li-ion batteries can cause long-lasting fires that are very difficult to extinguish. The North Collier firefighters reported one EV fire that reignited several hours after they thought it had been put out. In another instance, the South Trail Fire and Rescue District in Florida’s Lee County had to ask its Facebook followers to refrain from calling 911 about a Tesla submerged in a water-filled ditch, where the firefighters had left it to soak and ensure it wouldn’t reignite.

“When batteries of electric vehicles heat to the point of fire, it takes hours of copious amounts of water to extinguish,” the firefighters explained in an October 2 Facebook post.

A Tesla takes a bath after an EV fire caused by exposure to seawater from Hurricane Ian. (Source: South Trail Fire and Rescue District via Facebook.)

There’s a reason it takes so much water to put out a Li-ion battery fire. Lithium is highly flammable and reacts with most extinguishing agents including water, carbon dioxide, and carbon tetrachloride. It bursts into flame at 180°C and reacts with almost all gases as well as with asphalt, wood, sand, asbestos, and more. Large lithium fires should be treated with dry sand, dry chemicals, soda ash and lime, or by moving the lithium to a safe location and letting the fire burn itself out, according to the U.S. National Oceanic and Atmospheric Administration’s CAMEO chemical database.

What Causes Saltwater Battery Fires?

Pure water is an excellent insulator, but impurities make it a conductor. Saltwater is much more conductive than pure water. Salt dissolves in water to create charged ions—positive sodium and negative chloride. When the water evaporates, the residual salt remains conductive and becomes a path for electric current to flow. In an EV battery pack, this could mean a short circuit between bus bars or other high-current components.

In practice, such a short circuit will not have the ideal zero resistance. If the actual resistance is relatively high, current will be low and heat will be generated slowly. However, since batteries are sealed, heat dissipation is difficult. Even slow heat accumulates in the battery and eventually triggers thermal runaway. A short circuit with low resistance—such as conductive salt bridges—is even worse, since it leads to much higher current than is safe for the battery. And when an EV is off, its battery’s protection circuits are off as well.

Oxygen, another crucial ingredient for fires, is readily available in Li-ion batteries. It’s in the electrolyte, separator, and cathode, allowing batteries to ignite even when they’re not exposed to air. The hottest cell will rupture and spread burning particles, molten aluminum, and copper from the electrodes. Outside the battery pack, fire is fueled by hydrogen gas, carbon monoxide, and hydrocarbon chains generated by the thermal runaway. The fire is constantly renewed by the molten aluminum and copper particles. Even when the fire is extinguished, the salty short circuits may still exist and lead to re-ignition.

Solving the Saltwater Challenge for EVs

EV makers have an unfortunate tradeoff when it comes to powering their cars. Many features that make batteries desirable for EVs also make them a greater fire risk. For example, high energy density is good for vehicle range and size, but in the event of a short circuit it will maintain a high current flow and create more heat.

The EV industry is also shifting towards higher voltage levels. Today’s EVs use around 400 volts, but the industry is on track to double that within the next few years. Higher voltage allows for lower current, lower heat, longer driving range, faster charging, and lower weight. However, higher voltage brings a higher risk. In the event of a short circuit, the higher voltage will run a higher current and generate more heat in the cells.

Although the EV fires caused by Hurricane Ian have raised concerns, advocates remain confident in the technology. “We are absolutely concerned about any safety issues regarding electric vehicles, it’s just that they must be put in context,” said Marc Geller, a spokesperson for the Electric Vehicle Association, in an E&E News article from October 21.

Geller continued: “One Tesla fire gets more news than 10,000 gasoline car fires, whether it’s because people are super interested in Tesla or because people are still fighting the battle to suggest that EVs are not ready for prime time or not good.”

The fact is that EV technology is still young, and engineers haven’t sufficiently addressed thermal runaway, the Achilles’ heel of Li-ion batteries. Most of the current efforts to increase EV safety are based on battery management systems, controllers, sensors, and protection circuits that are only active when the EV is on, not parked in a Florida garage. Powering these circuits when the EV is off is not an easy answer, as it will discharge the battery.

Another approach is to protect batteries from dirt, water, and humidity with a good seal, but even this isn’t as straightforward as it seems. Sealing can cause problems for cooling and make thermal runaway more likely.

Could the solution be switching to alternative battery chemistries, such as lithium iron phosphate or sodium-ion batteries? Perhaps. Both of these chemistries have less fire risk than current Li-ion batteries, but they also have drawbacks including lower energy density and higher weight.

Ultimately, the saltwater flooding problem is still waiting to be solved. It’s one more pitstop that automotive engineers must take on the road to perfect the electric vehicle.

The post What Hurricane Ian Taught Us About EVs appeared first on Engineering.com.

With the capability to monitor, control and optimize battery performance, the battery management system (BMS) is key for high-performance batteries. Among the prime responsibilities of the BMS is to estimate the battery’s state of charge—but this crucial parameter is not always easy to measure. Two new research approaches may soon make the process easier.

Why Battery Management Systems Are Crucial

Batteries that operate in variable thermal conditions with frequent charging, deep discharging and high current peaks will have shortened life spans. A BMS can mitigate this. By measuring voltage, current, temperature and other variables, the BMS can optimize battery operation and control the charging/discharging process, thereby reducing the battery degradation process. The BMS keeps the battery system safe and reliable but also optimizes energy use (in an EV, this means more range).

An accurate BMS means an efficient battery system. (Source: Siemens.)

An important role of the BMS is to estimate the real condition of the battery, including its state of health (SoH) and state of charge (SoC). SoH indicates the level of battery degradation and provides critical information about performance and lifetime. Estimating the battery SoH in real time is very important for automotive applications. It’s useful for maintenance and replacement schedules and can be used as a fault diagnosis to help prevent hazardous accidents. SoH information can also help manage EV energy consumption to extend the range and the lifetime of batteries.

SoC, which refers to the remaining quantity of energy available in a battery, is calculated as the ratio of available charge to full charge, from 0 to 100 percent. EV efficiency is highly dependent on accurate SoC estimates, and accurate estimates require accurate current sensors in the BMS. The challenge is providing accurate measurements for a wide range of current values—from milliamps to tens of amps to greater than 100 amps in fast charging scenarios. Unfortunately, sensors that measure hundreds of amps cannot accurately measure milliamps—but a new sensor from researchers at the Tokyo Institute of Technology is looking to overcome that restriction.

New Research Could Lead to Better Battery Management

In September, the Tokyo Institute of Technology (Tokyo Tech) published the results of a research collaboration with Yazaki Corporation to develop a sensor that can measure currents in a wide range with high accuracy.

Led by Tokyo Tech’s Mutsuko Hatano, the researchers built a prototype composed of two diamond quantum sensors that they claim can estimate battery charge within 1 percent accuracy in EV applications. With existing solutions providing 10 percent accuracy, the new sensor has the potential to boost battery efficiency by 10 percent, according to Hatano.

“We developed diamond sensors that are sensitive to milliampere currents and compact enough to be implemented in automobiles,” Hatano said in a Tokyo Tech news release. “Furthermore, we measured currents in a wide range as well as detected milliampere-level currents in a noisy environment.”

The two diamond quantum sensors measure currents in and out of the battery and use a differential detection technique to eliminate common noise. Together they can detect currents as small as 10 mA within an operating temperature range from -40°C to +85°C—more than sufficient for EVs.

(Source: Tokyo Institute of Technology.)

Across the Pacific, researchers from the University at Buffalo have also been busy exploring a new approach to monitoring SoC: magnets. The researchers built a lithium-ion battery with a special magnetic material at one end. The magnetization of the material changes as lithium ions enter and leave it in the course of battery cycling.

“We can monitor the magnetism, and this enables us to indirectly monitor the lithium ions—the state of charge. We believe this is a new way to provide an accurate, fast, responsive sensing of state of charge,” said Shenqiang Ren, the lead researcher. The team published its findings in June under the title “Lithiating magneto-ionics in a rechargeable battery.”

While EVs get much of the attention when it comes to rechargeable batteries, these new approaches to SoC monitoring may enable better batteries in a wide range of applications. For engineers looking for that extra bit of battery power efficiency, this research is nothing short of energizing. 

The post Eye on Lithium: Two New Ways to Measure State of Charge appeared first on Engineering.com.

Lithium-ion batteries are everywhere, and for good reason. They are the most advanced battery technology commercially available today, offering high energy density, long life, light weight, fast charging and low maintenance. Lithium ions power everything from small consumer electronic devices all the way up to electric vehicles and battery energy storage systems.

However, lithium is a limited resource, and it’s getting harder to find. The price of lithium has skyrocketed over the past year, and many automakers—in the midst of an electric vehicle transition—are struggling to adapt.

The price of lithium carbonate has more than doubled since the beginning of 2022, according to trading on a contract for difference (CFD), which tracks the benchmark market for the commodity. The price is shown in Chinese yuan (CNY) per ton. (Source: Trading Economics.)

There is an urgent need to develop affordable and sustainable battery technologies, and researchers are exploring other elements on the periodic table. Earth abundant materials like sodium, magnesium, potassium and aluminum are among the most promising options.

But according to researchers from Rensselaer Polytechnic Institute (RPI) in New York, the best choice may be the one you can feel in your bones: calcium.

The Challenges of Calcium-ion Batteries

Calcium-ion is a promising alternative battery technology with the potential to be cost-efficient, sustainable and high performing. And unlike lithium, calcium is widely available at a low price. But the technology still has technical challenges that must be overcome.

For one thing, calcium ions are bigger and have a higher charge density than lithium ions. Calcium has multivalent metal ions, meaning that during battery operation, one ion will deliver two or more electrons. This increases the battery’s specific capacity, or charge density, a measure of electric charge per unit area of a surface (or per unit volume of a body). Higher charge density weakens diffusion kinetics and cyclic stability during battery operation. This problem doesn’t solely affect calcium-ion batteries—magnesium and aluminum ions have the same problem, but to an even greater extent. The reduction potential of calcium ions is also lower than for these other multivalent ions, which enables higher cell voltage of the battery.

One big obstacle to constructing a calcium-ion battery is finding suitable electrodes that can host the large and charge-dense ions. This is the challenge that researcher Nikhil Koratkar and his coauthors from RPI addressed in a paper published in Proceedings of the National Academy of Sciences (PNAS) in July 2022 called “Reversible and rapid calcium intercalation into molybdenum vanadium oxides.”

Big Channels for Big Ions

There are many ways to configure layers of molybdenum and vanadium oxides, which makes them a useful host for intercalating lithium ions. With their larger size, however, calcium ions don’t squeeze in quite as readily.

The RPI researchers experimented with several different molybdenum vanadium oxide (MoVO) structures to find a good fit for calcium ions. So-called orthorhombic and trigonal MoVOs proved the most effective, as they contain large hexagonal and heptagonal tunnels that present effective pathways for calcium diffusion.

Essentially, the big MoVO channels provide an easy way for calcium ions to go back and forth between the electrode and a water-based electrolyte.

“The higher ionic charge and the larger size of calcium ions relative to lithium makes it very challenging to insert calcium ions into the battery electrodes,” explained Koratkar in a news release issued by RPI. “We overcome this problem by developing a special class of materials called molybdenum vanadium oxides that contain large hexagonal and heptagonal shaped channels or tunnels that run through the material.”

In their experiments, the researchers demonstrated a specific capacity of 203 mAh/g at a charge rate of 0.2C and 60 mAh/g at 20C. The calcium-ion battery had a capacity fade rate of only ~0.15 percent per cycle.

The work is a promising step toward a much-needed alternative to lithium-ion batteries.

“Calcium-ion batteries might one day, in the not-so-distant future, replace lithium-ion technology as the battery chemistry of choice that powers our society. This work can lead to a new class of high-performing calcium-based batteries that use Earth abundant and safe materials and are therefore affordable and sustainable,” Koratkar said.

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