30 min read energy storage

Why are lithium-ion batteries so popular?

Why are lithium-ion batteries so popular?
Photo by Kumpan Electric / Unsplash

Table of Contents

In Brief

Lithium-ion batteries have gained popularity in a wide variety of technologies including mobile phones, laptops, power tools, e-scooters, electric vehicles and many other devices due to several key advantages:

  • High energy density: Lithium-ion batteries hold a large amount of power per kilogram of mass. This makes them ideal for electronics that need to be small and portable and for electric vehicles that need to have a light, compact power source.
  • Slow self-discharge rate: Lithium-ion batteries only lose about 2% of their charge each month. This means that one year after a full charge, they should retain about 75% of their power.
  • Long lifespan: Lithium-ion batteries can last around a decade before their total charge capacity drops to around 70% of their initial capacity. They can also endure between around 1500 to 3000 full charges and discharges before performance declines.
  • Versatility: Lithium oxide can be combined with different metals to create distinct batteries with different characteristics. This includes high power short duration batteries for power tools and long duration, moderate power batteries for phones and tablets.

To learn more about lithium-ion batteries and how they compare to other batteries and energy storage solutions, I invite to continue reading below.

Introduction

Over the past thirty years, lithium-ion batteries have played an essential role in powering our modern lifestyle. The high amount of electricity that they can deliver in a small package has allowed us to break free from cords and stay connected to our professional and personal lives through smart phones, laptops, and tablets even while on the move.

From tiny batteries powering our ear buds for several hours to larger systems that keep cars and busses rolling for hundreds of kilometres, the high energy density of lithium-ion batteries has become essential in our day-to-day use of mobile technology and consumption of electricity.

But when we think of electricity distribution rather than electricity consumption, we increasingly think of lithium-ion batteries in the context of stationary power. That’s because lithium-ion batteries are no longer just used in portable devices and electric vehicles. They are being employed at large scales to supply electricity to homes, factories, mines, and even power grids. As of 2020, lithium-ion dominated the battery storage industry making up 93% of the market.[1]

In this post, I explore how a battery technology that was originally developed to power portable electronic devices has come to play an important role in storing and discharging electricity from power plants. I also look at the future of lithium-ion batteries for large-scale energy storage considering whether it is the best option or if other technologies may become more attractive for energy storage.

Infographic of sizes of lithium-ion batteries in Wh, kWh and MWh.

What is a Lithium-Ion Battery?

Most of us own multiple devices with built-in lithium-ion batteries. It is likely that we use these products on a daily basis without giving much thought about the technology that is powering them. But the innovations in rechargeable lithium-ion batteries have had a major influence in how we engage with technology and the digital world.

Lithium-ion batteries have become so important and so common due to the characteristics of lithium as a metal. Lithium is a tiny metallic element with low density and high electrochemical capacity. This means that it can hold a high amount of electricity in a small, lightweight package.

Each lithium-ion battery is made up of electrochemical cells. These cells contain two electrodes between which lithium ions move. One electrode, called the cathode, is comprised of an aluminum conductor coated with a combination of lithium oxide and another metal, such as nickel, cobalt or iron. The other electrode is called the anode. It is made up of a copper conductor coated with a carbon, typically graphite, which can hold a high number of lithium ions.

The cathode and the anode are surrounded by an electrolyte, which contains lithium salt and is often in liquid form but can also be a gel or solid. The electrolyte reacts with the chemicals in the electrodes to release lithium ions—atoms of lithium that have an electrical charge due to an unequal number of electrons and protons. The electrolyte also facilitates the movement of these ions from one electrode to the other.

When the battery is supplied with electricity from an external source (i.e. when it is being charged), the lithium ions in the cathode move across the electrolyte, through the semi-permeable separator and attach to the anode.

The movement is reversed when the battery is used to provide power. The ions move from the anode back to the cathode. At the same time, some electrons become separated from the lithium ions.

These electrons move along a conductive circuit outside of the cell.[2] The circuit becomes a complete pathway when the battery is attached to a device requiring electricity. Electrons move along this pathway and travel from the copper conductor at the anode to the aluminum conductor at the cathode. This flow of electrons produces electricity.

Once the anode becomes depleted of ions, the battery ceases to discharge electricity. Now it is time to recharge the battery. This means sending the ions that have returned to the cathode back to the anode.

Diagram of a Lithium-Ion Battery Cell

What are the Types of Rechargeable Batteries?

Lithium-ion batteries are not the least expensive rechargeable battery nor are they the oldest. In fact, while lithium-ion batteries have only been commercially available since the 1990s, the lead-acid rechargeable battery was developed in France in 1859 and has been commercially produced since the 1880s. Soon after, the nickel-cadmium battery was created in Sweden in 1899.

These two types of batteries would become the most popular forms of rechargeable batteries for the next century. Lead-acid batteries have been used primarily for utility purposes, such as back-up power and in small vehicles. Nickel-cadmium batteries have been used more extensively in smaller devices such as tools and consumer electronics. Since the early 1990s, nickel-cadmium battery technology has been surpassed by nickel-metal-hydride batteries, which are much less toxic and can provide electricity for longer durations of use.

It was only in 1991 that the first lithium-ion batteries—produced by Sony Corporation—reached the commercial market. But, within the subsequent three decades, lithium-ion batteries have found widespread use across consumer and industrial applications. There are several characteristics of lithium-ion batteries’ composition and performance that explain its favourability versus other types of rechargeable batteries:

Energy Density

Energy density refers to the watt-hours per kilogram or the amount of electricity that a battery can store in relation to its mass.

  • Lithium-ion batteries average around 150 Wh/kg
  • In contrast, the energy density of lead-acid batteries is around 30 Wh/kg
  • For nickel-cadmium batteries, the average energy density is 60 Wh/kg
  • Nickel-metal-hydride batteries offer an improvement over nickel-cadmium batteries averaging around 90 Wh/kg

High energy density is critical for both small electronics and electric vehicles. For example, in a mobile phone, a small battery that holds a large amount of electricity allows for more space and provides more energy to sophisticated hardware and cameras while also powering advanced applications. For electric vehicles, a high ratio of energy per kilogram of battery is crucially important for reducing the weight of a vehicle.

If a cellphone were to be powered by a nickel-cadmium battery rather than a lithium-ion battery, the manufacturer would have to choose to comprise either the energy—meaning the device would need to be less powerful or charged much more frequently—or size, which would mean that a mobile phone would have to be much larger and much less portable.

Charging Cycles

Rechargeable batteries save the hassle of having to replace batteries in a device, but they do not last forever. The process of charging a battery eventually degrades the electrodes after hundreds or thousands of charge cycles. The amount of wear varies significantly across battery types:

  • Lithium-ion batteries can endure over 1000 charges before the performance of the battery begins to noticeably decline
  • Nickel-cadmium batteries are considered a fairly durable battery and can also withstand around 1000 charge cycles
  • Lead-acid and nickel-metal-hydride batteries, however, will last half as many charge cycles (~500) until their performance declines  

Table 1: The Advantages of Lithium-Ion Batteries

Lithium-ion batteries compared to other rechargeable batteries

Lithium-ion Research and Development

The advantages of high energy density and comparatively long lifespans make lithium-ion batteries the most popular option for most consumer electronics. Perhaps even more consequentially, they are the choice of power for electric vehicles. This important is because the development of lithium-ion batteries for use in electric vehicles has spurred much of the research and development that has occurred in the past two decades.

While greater energy density and longer power supplies gave lithium-ion batteries a clear advantage over competing batteries in the consumer market of phones and computers, lithium-ion batteries for electric vehicles faced a much different competitor. They were not competing against other batteries, but rather, against petrol and diesel.

For electric vehicles to become an attractive alternative to fossil fuel vehicles, lithium-ion batteries needed to bring down their costs and prove that they could power a vehicle over a range of several hundred kilometres. These requirements led to years of collaboration between electric vehicle manufacturers who had the capital to invest in EV battery technology and R&D organizations that had been working on improving lithium-ion batteries.

Through the partnerships between researchers and the car industry, technological advancements, greater economies of scale, and improvements in manufacturing efficiency have brought down the cost of lithium-ion battery production by 90 percent between 2010 and 2019.[3]

These advancements in lithium-ion technologies and economies of scale have made electric vehicles more affordable and, in jurisdictions with credits and tax incentives for EVs, have even made them cost competitive with combustion engine vehicles.

Yet, as anyone who has shopped for and compared EVs will immediately notice, there is a wide variety of prices, charging times and ranges of electric vehicles. These variations usually come down to the design and construction of the battery packs, including the size and number of cells. Another key factor is the material composition of the lithium-ion battery.

As mentioned earlier, the electrodes in the cells of a lithium-ion battery are comprised of a lithium graphite anode and a cathode. The cathode contains a compound of lithium oxide and another element, such as iron, magnesium, cobalt or other metals. The choice of compounds and their proportions determine the characteristics of a lithium-ion battery, such as cost, performance and lifespan.


6 Types of Lithium-Ion Batteries

1. Lithium Nickel Manganese Cobalt Oxide (NMC)

  • One of the most common and lower cost types of lithium-ion batteries
  • The ratio between nickel, manganese and cobalt can be adjusted to produce different performance attributes and costs     

  a. A higher proportion of nickel produces a battery with a lower cost, longer lifecycle, high specific energy and greater energy density

    b. A higher proportion of manganese produces higher specific power and more durability

  c. Cobalt provides high energy density. It also stabilizes nickel, which is susceptible to thermal runaway.

  • The high charge lifecycle of NMC batteries makes them a popular choice for devices that require frequent charging and a high level of safety:

  a.   Medical devices

  b.   Electric vehicles

  c.   Energy storage systems

2. Lithium Iron Phosphate (LFP)

  • One of the safest, most durable and least expensive lithium-ion batteries
  • LFP has a high heat threshold and, therefore, a lower risk of thermal runaway
  • Sensitive to cold temperatures, which reduces its performance
  • Low specific energy but high specific power
  • Comparatively lower energy density
  • Lower toxicity than batteries containing cobalt and/or nickel
  • Due to their high durability, they can provide up to 3000 charge cycles and are more commonly found in:

  a. Electric vehicles

  b.   Energy storage systems

3. Lithium Nickel Cobalt Aluminum Oxide (NCA)

  • NCA batteries provide high specific energy and moderate specific power
  • Higher cost
  • The addition of nickel increases toxicity and risk of thermal runaway
  • Due to its ability to provide power over a long period, they are popular for electric vehicles

4. Lithium Manganese Oxide (LMO)

  • LMO is inexpensive but has a short lifespan
  • It provides high specific power
  • LMO batteries offer higher safety than lithium-ion batteries with nickel

5. Lithium Cobalt Oxide (LCO)

  • Comparatively, a lower cost battery
  • High specific energy and low specific power
  • LCO are commonly used in consumer electronics that require longer duration of use but lower power, such as laptops, tablets, cameras and phones
  • They have a higher risk of thermal runaway, which is increased if they are fully charged, and a shorter lifespan

6. Lithium Titanate (LTO)

  • LTO batteries replace the graphite anode with a lithium titanate material to provide:

  a.   Rapid charging

  b.   Greater performance range

  c.   Higher safety

  d.   Longer lifespan

  • The cathode used in LTO batteries is either lithium manganese oxide (LMO) or lithium nickel manganese cobalt (NMC)
  • The disadvantage of LTO is their lower energy density and higher cost—more than double the average price of lithium-ion batteries in general
  • They are primarily used in military and aerospace applications

The improved knowledge and manufacturing capacity of lithium-ion batteries have led to important improvements over the last decade. The energy density of EV batteries has doubled,[4] which has enabled greater driving range making them much more attractive to buyers.

The number of EVs sold globally in the three years since 2019 has nearly doubled and they are projected to make up half of all vehicle sales by the end of the 2020s.[5] This growth will precipitate the development of well-established supply chains and infrastructure to support a robust, full cycle lithium-ion industry.

Lithium-Ion Batteries and Renewable Energy

In addition to the greater operation and performance of lithium-ion batteries in recent years, the improvements in efficiency and durability have also extended their lifespans. This gives automakers the confidence to guarantee a replacement of batteries if they fail or significantly decline in charge capacity within a decade of normal use. Older batteries that have reached the end of their life powering cars sometimes find a second life as energy storage in residential or utility applications.

Battery warranty information of electric vehicles

Lithium-ion batteries in EVs usually store and discharge power frequently moving a heavy vehicle over thousands of kilometres for a decade until until their capacity declines. However, once retired, they no longer endure these heavy performance demands and can still offer years of productive service as stationary backup power.

They are particularly useful for intermittent renewable energy systems, such as solar and wind. On their own, these sources of power cannot respond quickly to fluctuations in electricity demand. But when paired with batteries, renewables can begin to operate like on-demand power supplies, such as natural gas plants, especially as the price of wind and solar decreases.

In the decade since 2010, the cost of solar energy underwent a decrease of 90%.[6] Alongside a less steep decline in the already more affordable wind power, solar and wind have become the least expensive forms of energy in many parts of the world.

Table 2: The Price Decrease of Solar and Wind Energy (2021 vs. 2010)

Price decrease of solar and wind energy (2021 vs. 2010) [Table 2]

Table 3: Cost of Solar and Wind Energy Projects Versus Coal and Natural Gas

The cost of solar and wind energy projects vs. coal and natural gas [Table 3]

This price drop has led to a large increase in the deployment of solar photovoltaic plants and wind turbines. In some regions, the large share of renewables produces an occasional oversupply of electricity that exceeds demand. To prevent the excess electricity from overloading the grid or forcing utilities to pay for electricity that isn’t needed, the renewable energy plants are disconnected from the system. This intervention is called curtailment.

The issue of curtailment is particularly acute in seasons with greater energy production and lower demand, meaning spring and summer. This causes thousands of megawatt hours of clean electricity to be produced but not used. While this potential electricity is being wasted during times of peak production, during the evening hours or winter when renewable energy production is lower, grids revert to relying on fossil fuels to meet energy demand.

One solution to addressing the imbalance between energy supply and demand is energy storage. With the cost of renewable energy production and lithium-ion batteries dropping rapidly, it is becoming more economical to build facilities that pair renewables with large-scale batteries that store excess supplies of electricity.

Today, the demand for energy storage is so great that lithium-ion battery systems are being manufactured specifically to meet this need. Battery energy storage system modules can be shipped and deployed nearly anywhere in the world, even in locations far from major electrical grids. In addition, extra modules can be added to an existing system to increase their energy storage capacity.

To maximize the economic benefits of a combined renewable energy and energy storage system, AI-assisted software can be used to model ideal times to charge battery energy storage systems (BESS) and determine when these systems should discharge electricity.

These operations are based on local conditions such as seasonal weather patterns and daily hours of peak demand for electricity. By supplying electricity to the grid when energy demand is greatest—and thus most expensive—batteries not only modulate frequency but also keep electricity costs lower.

One of the first grid-scale battery energy storage systems to be built is the Hornsdale Power Reserve, which is owned by Neoen Australia and located in South Australia. The plant has a capacity of 150 MW and stores electricity in lithium-ion batteries. Hornsdale was originally constructed as a 100 MW facility and was scaled up to its current capacity in 2020. Electricity is supplied to the system from the 315 MW Hornsdale wind farm.

The Hornsdale Power Reserve is capable of providing grid stabilization by modulating frequency deviations. It can provide electricity for a period of a few hours in the event of a blackout and absorb excess electricity when production exceeds demand.

Since the South Australian BESS came online in 2017, several larger facilities have since been built as local and regional grids aim to replace coal and gas power plants with renewable energy. Among these projects is a 400 MW power reserve at Moss Landing Harbor in California. The lithium-ion battery energy storage system was installed on the site of a retired gas power plant and is owned and operated by the Texas-based energy company Vistra using LG Energy Solution batteries.

The Moss Landing Vistra facility is one of several grid-scale lithium-ion energy storage systems that have been constructed across California and Texas since 2020. Additional plants have also come on line in other southwestern states, such as Nevada and Arizona, where wind and solar energy potential is abundant.

What are the Safety Concerns of Lithium-Ion Batteries?

In the near future, the demand for lithium-ion batteries is projected to grow rapidly. The market share of electric vehicles continues to increase and, as the attractiveness of wind and solar power becomes greater, the energy storage industry will become a major player in the transition to clean electricity. Battery energy storage systems may also increasingly be employed in individual homes and buildings to protect against power outages.

However, some lithium-ion batteries are less suited to residential usage. Certain batteries carry a higher risk of thermal runaway and some jurisdictions prohibit the indoor installation of stationary batteries containing nickel, including in garages. In addition, cobalt and nickel have a higher level of toxicity than other metals used in lithium-ion batteries and could pose a danger to human health if damaged.

Furthermore, the use of nickel and cobalt raises concerns about mining and supply chains. Indonesia is by far the largest producer of nickel in the world. But mining practices in the country create problems of environmental contamination from tailings and high greenhouse gas emissions. The country has also restricted the export of raw nickel in order to stimulate a domestic nickel processing and refining industry.

Meanwhile, cobalt-mining practices have received even greater attention and criticism. Over two-thirds of cobalt production occurs in the Democratic Republic of the Congo as a by-product of nickel and copper mining. The lack of strong regulations around labour and environmental standards have led to toxic exposure to the local environment and communities; violent conflict; incidences of child labour; and negative impacts to the health of miners.

These issues have encouraged governments, car manufacturers and energy storage companies to shift to lithium-ion batteries that have either no cobalt and nickel or lower quantities of these elements.

As an alternative, lithium iron phosphate batteries have become more popular in the past couple of years. Due to their higher durability and the relative mineral abundance of iron and phosphate, they have a longer lifespan and are less expensive. They are also much safer since they are less toxic and present a low risk of fire. In contrast to nickel-based batteries, they can safely be used indoors for stationary energy storage. One downside of lithium iron phosphate batteries is their lower energy density.

The recent shift towards lithium iron phosphate batteries is just one way that the lithium-ion battery industry continues to evolve in response to the changing energy market. Within the past decade, the rapidly growing demand for lithium-ion batteries have encouraged several major technological advancements:

  • Greater manufacturing capacity and techniques have significantly brought down prices;
  • The improved safety and durability of lithium-ion batteries has reduced risks of fire and damage;
  • The power and energy that they can provide has increased; and
  • Charging times have become shorter.

Many of these trends will likely continue as manufacturers innovate with new materials and production methods. One such potential advancement is the use of silicone as the anode. Silicone can hold a greater amount of lithium ions than graphite, which is currently used in the anode. This would increase the energy density of lithium-ion batteries. However, the major obstacle that must be overcome is that silicone breaks down more quickly than graphite. This means that if it were to replace graphite as the anode, the batteries would have a much shorter lifespan.

Another goal of researchers is to produce a solid-state lithium battery. This would entail using a solid lithium electrode and replacing the liquid electrolyte with solid ceramic layers. These changes would improve energy density, reduce charging time, and extend the number of possible charge cycles. Replacing the liquid electrolyte would also reduce the risk of fire.

Challenges of the Lithium-Ion Industry

Despite the success of lithium-ion batteries in the EV and energy storage markets, there are some challenges that the industry faces. Firstly, lithium-ion batteries are considered a form of short-term energy storage. When delivering their full power capacity, they provide around 4-6 hours of electricity. Technological improvements may double or triple the duration of energy they provide to around 10-15 hours.

This will be a sufficient amount of energy for electric vehicles and back-up power in the case of outages. However, grid-scale facilities will need to incorporate seasonal energy storage if they hope to replace coal and gas power plants completely. This means storing supplies of energy to last weeks or even months. The amount of batteries that would be required to fulfill this need would be massive and unrealistic.

Secondly, the amount of lithium that will need to be mined and processed will increase exponentially over the next decade to meet the demand for electric vehicles and batteries. Fortunately, the majority of high-grade production of lithium occurs in stable, democratic countries with well-developed mining industries: Australia (48.7% of global production in 2020) and Chile (21.9%).[13] When comparing known reserves of lithium, the shares located in these countries are nearly the inverse: Chile has 43.7% and Australia has 22.3%.

One of the reasons why Australian production of lithium is more than double Chilean production comes down to the different nature of their lithium deposits. In Australia, lithium is found in hard rock and can be obtained through conventional mining and processing methods. In Chile, the lithium is found in groundwater located under salt flats. Extracting the lithium requires pumping large quantities of this lithium brine into pools above ground and letting the water evaporate. This process has a damaging impact on the local ecosystem and worsens water security in one of the driest regions of the planet.

While the large majority of lithium production occurs in Australia and Chile, lithium refining is dominated by one country—China—which controls 60% of lithium refining.[14] Ensuring a secure and reliable lithium supply chain will require diversifying lithium processing and refining to other nations.

Thirdly, the issue of processing lithium-ion batteries once they are no longer operational will need to be addressed. Many of the minerals contained in the battery cells, including lithium and rare elements like cobalt have the potential be recycled. This means that they can be salvaged and reused in the production of new batteries. The processes for recovering lithium are still relatively new, but as more lithium-ion batteries reach the end of their lifespan, there will be both a need and an opportunity for profitable large-scale recycling.

Finally, there is the question of thermal runaway. Misuse or unintentional damage to a lithium-ion battery, such as a car accident, can cause an exothermic reaction between the energy dense materials in a battery cell that suddenly increases its temperature. This can lead to the battery failing, releasing toxic gases, and—in some cases—combusting into flames.

In the past few years, there have been multiple news stories of EV recalls and, more often, fires caused by electric scooters and bicycles—many of which contain cheaply made batteries. So far, the incidences of thermal runaway have not reached a level of concern that would slow the growth of the lithium-ion industry.

In the context of the energy industry, accidents related to lithium-ion batteries have been much less severe than those caused by hydrocarbons, especially natural gas which has destroyed entire buildings and killed hundreds of people even in countries where strong safety standards exist.

While the safety concern of thermal runaway has not been a major hindrance to lithium-ion battery production, the phenomenon does present a risk to a key factor in energy distribution: reliability. There have been fires at grid-scale lithium-ion battery plants in Arizona, California and Victoria (Australia). While these events did not cause damage beyond the battery packs, they did lead to public warnings of toxic fumes, temporary shutdowns, and investigations.

Improvements to the design of these battery plants, including the use of coolants to limit overheating, fire-resistant insulation to prevent the spread of flames, and the use of lithium iron phosphate batteries, which are less toxic and less susceptible to thermal runaway, may help to maintain confidence in the technology.

Energy Storage Alternatives

Some key questions for the future of energy storage include:

1.    How do we diversify battery energy storage system technologies so that we are not as reliant on one mineral: lithium?

2.    Can we produce long-term seasonal energy storage that is reliable and cost-competitive with natural gas?

To address the challenges and limitations of lithium-ion batteries and meet the demand for energy storage, it will be important for other technologies to achieve similar economies of scale and technological development.

Many alternative energy storage systems already exist and have been used for decades. But, they have failed to achieve the same levels of research and production as lithium-ion batteries, which have benefitted from massive investments from automobile manufacturers. This situation has the potential to change if the proliferation of variable renewable energy facilities leads to the emergence of a large energy storage industry.

Below, we will look at three technologies that could gain popularity and capture a share of the energy storage market in the coming years:

1.    Sodium-sulfur batteries

2.    Flywheels

3.    Hydrogen power

Sodium-Sulfur Batteries

Of these three options, sodium-sulfur batteries are the most similar to lithium-ion batteries. They receive electricity from an external source and store it as electrochemical energy before converting that energy back into electricity when used to power a device. As their name indicates, their electrodes are made of sodium and sulfur—two of the most abundant and geographically dispersed elements on the planet. In addition to being inexpensive and accessible, the materials are also non-toxic.

The major disadvantage of sodium-sulfur batteries is their high operating temperature of between 300° and 350° Celsius. Sodium is also naturally corrosive. This means that sodium-sulfur batteries require strong safety measures in terms of how they are contained and handled.

Under these conditions, they are only suitable for stationary energy storage. So far, one Japanese company (NGK Insulators) is responsible for most of the global production and deployment of sodium-sulfur batteries. This has been undertaken primarily in Japan with recent installations constructed in the Middle East. Given their associated risks and limitations, sodium-sulfur batteries have been unable to achieve the economies of scale of lithium-ion batteries, which have a much broader range of applications.

Researchers working in the area of sodium-sulfur batteries are tackling the issue of the high operating temperature. A lower temperature system that reaches commercial production could rival lithium-ion batteries not only as an alternative for energy storage but also as a battery for electric vehicles.

Room temperature sodium-sulfur batteries that are currently under development demonstrate the ability provide greater energy density and better specific energy than lithium-ion batteries. This would give EVs a longer range and a lighter, smaller battery, thus making them more attractive in terms of performance than current EVs. The lower raw material cost of sodium and sulfur would also make them less expensive than lithium-ion EVs when mass production develops. This would make them cost competitive with fossil fuel vehicles even without tax credits for consumers.

Flywheels

While sodium-sulfur batteries do not yet come to mind when thinking about cars, another technology—flywheels—are closely associated with managing the power of vehicles. Flywheels consist of a rapidly spinning rotor that stores kinetic energy. They play an important role in balancing the power fluctuations of a car’s engine when accelerating and decelerating or shifting gears. This creates a smoother drive and reduces wear on the mechanical components between the engine and the wheels.

The same principle of smoothing power fluctuations can be applied on a larger scale when flywheels are used for energy storage. Flywheels can respond quickly to excess supplies of electricity from wind turbines and store that energy for tens of minutes or potentially a few hours. The energy is stored in the rapid motion of the spinning rotor, which reaches rates as high as between 50,000 to 100,000 RPM.

The momentum of the rotor (and thus the energy stored) is maintained through the design of the rotor and the container in which it is stored. A rotor with magnetic bearings combined with a vacuum container minimizes inertia and resistance. Constructing a rotor with most of its weight placed on the outer rim also enhances rotational momentum.

When there is a drop in electricity production from variable renewable energy sources, the rotor decelerates and the flywheel can quickly discharge the stored kinetic energy. This energy is sent to a motor-generator where it is converted back into electricity.

The major advantage of the flywheel is its materials and construction. It is a mechanical rather than electrochemical device, which means that it can be constructed from conventional materials, like carbon-fibre, steel and concrete, and does not require rare or toxic minerals. Flywheels are robust and can endure 100,000 to 200,000 full charge and discharge cycles in contrast to lithium-ion batteries, which only average 1,000 to 3,000 cycles before their performance degrades. They can also operate well at both high and low temperatures.

However, flywheels, unlike sodium-sulfur batteries, are not directly analogous to lithium-ion batteries in terms of how they operate. While they are both considered short duration energy solutions, lithium-ion batteries can deliver 4-6 hours of power. Flywheels, on the other hand, provide between several seconds to up to 15 minutes of electricity.

As an energy storage system, flywheels are a robust and dependable technology that can discharge a large amount of power for a short period. They are ideally suited for handling frequency disruptions that last seconds or minutes since they can respond rapidly and endure much more wear and use than electrochemical batteries.

Hydrogen Power

Hydrogen energy and lithium-ion batteries have often been characterized as competitors, especially in the race for market share between fuel cell electric vehicles (FCEVs) powered by hydrogen and battery electric vehicles (BEVs) powered by lithium-ion. At, the moment, BEVs have taken a clear head start, but proponents of FCEVs contend that hydrogen will play a major role in the future of transportation.

Contrasting the characteristics of hydrogen energy with those of lithium-ion batteries can help us to answer some key questions:

1.    Why has the lithium-ion battery industry developed more quickly than the hydrogen industry?

2.    Could the sale of FCEVs surpass BEVs in the future?

3.    Are hydrogen and lithium-ion competitors or are they distinct solutions to different problems?

Hydrogen fuel cells and lithium-ion batteries share the advantage of producing electricity while emitting no greenhouse gases. The major difference between a fuel cell and a battery is that the chemical reactants that interact to produce electricity are permanently contained within a battery while a fuel cell is fed these reactants from an external source.

For a hydrogen fuel cell, the two reactants are hydrogen and oxygen, which are supplied to the anode and cathode respectively. Electrons from the hydrogen atoms travel along a conductive wire outside of the fuel cell from the anode to the cathode generating electricity.

Since the hydrogen comes from an external source, the experience of refuelling a fuel cell vehicle is much more similar to fuelling a fossil fuel vehicle. The operator of a vehicle would travel to a service station and pump hydrogen into their fuel cell within a few minutes. In contrast, BEVs typically require between a half-hour to a couple of hours to fully charge.

As a gas, hydrogen also shares other similarities with hydrocarbons. Like natural gas, it can be transported through pipes to be burned for heating or to be used in gas power plants to produce electricity.

So, if a fuel cell electric vehicle can be refuelled much faster than a battery electric vehicle and hydrogen can be burned for heat and electricity, why has it not taken off as a major source of energy?

The first factor that limits large-scale development of clean hydrogen is the production process. There are several methods for producing hydrogen that create little or no CO2 emissions. However, most of them are still in the research and testing phases. These include methane splitting (separating hydrogen from carbon under high heat), thermochemical water splitting (using heat and chemicals to separate hydrogen from water), and biological processes like photosynthesis of algae and biogas production.

The only commercialized method of producing hydrogen without emitting large amounts of greenhouse gases is water electrolysis. This process uses electricity to split water into hydrogen and oxygen. When renewable energy is used to produce the electricity required, zero-emission hydrogen can be made.

Electrolyzers are promising tools to aid in decarbonization, but they face challenges. The industry is still relatively small and the economies of scale needed to bring down manufacturing costs have not yet been achieved. In the short term, electrolysis will be uncompetitive with traditional fossil fuel based methods of hydrogen production.

A further problem is that the energy efficiency of electrolyzers is only around 60-80%.[15] This means that up to 40% of the electricity input is lost in the process of creating hydrogen. There are further efficiency losses during transportation and through the conversion of hydrogen back into electricity.

Additionally, FCEVs require significant infrastructure to be built out before it becomes feasible for individuals to use them for every day use. In contrast, BEV operators can be autonomous in terms of power since they can install a charger at their own home. Chargers are also becoming readily accessible in public spaces since they are easy and safe to install. Hydrogen FCEV drivers, however, would need to rely on the installation of a third-party hydrogen fuelling station. Very few of these currently exist, which greatly limits the growth of the FCEV market.

These inefficiencies have given critics of hydrogen an argument against FCEVs and hydrogen for electricity production. If the goal of decarbonization is to reduce the greatest amount of greenhouse gas emissions from being released, then employing the technologies that most efficiently produce clean energy is more optimal. So, instead of using electricity to create hydrogen, it would be more effective and impactful to send that electricity directly to the grid rather than losing half or more of it through hydrogen production and distribution.

Despite these shortcomings, the clean hydrogen industry has witnessed a spike in activity since 2020 as governments across the world implement hydrogen strategies and pour billions of dollars into hydrogen investments. This is because hydrogen is considered a solution to decarbonization in many sectors and applications where no alternatives currently exist.

One such application is long duration energy storage (LDES). Energy storage systems, like batteries and flywheels, can charge and discharge several hours of electricity to modulate supply and demand during the day. But many locations, particularly in areas farther from the equator, require seasonal energy storage to compensate for reduced sunlight and increased energy usage during the winter months.

Since hydrogen has a very high energy density and can be stored in gas or liquid form, similar to natural gas or oil, large quantities can be stored for long periods in underground reservoirs or in steel tanks. The hydrogen could then be dispatched on demand to a fuel cell or power plant as needed. In the longer term, hydrogen is a potential option for maritime shipping and long haul flights. These are applications where the use of batteries as a primary source of power is likely unfeasible.

A comparison of the characteristics of lithium-ion batteries and hydrogen energy suggests that, rather than viewing these technologies as competitors, it is better to consider them as complementary solutions to decarbonization. Each comes with its own opportunities as well as limitations. In some instances, the strengths of one can compensate for the weaknesses of the other and vice-versa. This not only applies to distinct industries and operations, but also includes hybrid power systems that combine hydrogen and batteries.

One example of a hybrid energy system that demonstrates how renewable energy can be supported by multiple types of energy storage systems is the Raglan mine in the arctic region of Nunavik in Quebec, Canada. The energy system is operated by the TUGLIQ Energy Company—with financial support from the Government of Canada—as a pilot demonstration project at Glencore’s Raglan nickel mine.

Like many remote northern communities in Canada, power generation depends on diesel that is shipped in from hundreds of kilometres away. This situation exposes these communities and their economies to risks related to the volatility of fossil fuel prices, the impact of weather on transportation, and the environmental problems of shipping and burning fossil fuels. The installation of renewable energy systems in these regions can help to mitigate these impediments to energy security and economic development.

In the case of the Raglan mine, local power is now partly generated by a wind turbine connected to a flywheel, lithium-ion batteries, an electrolyzer, and a fuel cell. The system is managed by an automated program that uses predictive algorithms to maximize the wind energy input.

Each of the energy storage systems plays a different role in maximizing the proportion of wind power to achieve up to 50 percent renewable energy penetration and to minimize stress on the infrastructure. The flywheel, the most robust part of the system, responds rapidly to fluctuations in the wind. The lithium-ion battery provides short-term energy storage and acts as a starter for the diesel generators and fuel cells. The electrolyzer produces hydrogen, which is stored in steel tanks and provides long-term energy storage. Finally, the fuel cells convert the hydrogen back into electricity when required.

The pilot project is intended to demonstrate the potential for local, renewable energy production in regions that are isolated from energy infrastructure and which rely on fuels transported from larger centres hundreds of kilometres away. However, we can also extrapolate this example to consider future energy systems more broadly.

Rather than viewing clean energy technologies as competing options, we can consider how they can work together to complement each other. This can help us to design systems that are more efficient, reliable, robust, and that reduce energy waste.

Table 4: Comparison of Lithium-ion Batteries with Sodium-Sulfur Batteries, Flywheels, and Hydrogen Power

Comparison of energy storage systems [Table 4]

Conclusion

At the beginning of this post, I proposed two questions related to lithium-ion batteries:

1.    Why have lithium-ion batteries become the dominant form of battery energy storage?

2.    What is the future of lithium-ion batteries for energy storage?

The most attractive feature of lithium-ion batteries is its energy density. Its ability to store a relatively large amount of energy within a small package compared to other batteries makes it a versatile storage solution that can deliver power to many different technologies. This has led to achieving economies of scale in the manufacturing of lithium-ion batteries that improve production methods and decrease costs.

The adoption of lithium-ion batteries by the automotive industry for electric vehicles accelerated the advancement of the technology. The need to compete with fossil fuel vehicles on measures of cost, range, charging time and safety has spurred investments in research that have rapidly improved the capabilities of lithium-ion technology.

Continued research will allow drivers to charge their vehicles faster, go farther on a single charge and pay less for an EV than a combustion engine vehicle. But as lithium-ion batteries are increasingly employed in large-scale applications, such as industrial power back up and grid support, we begin to see limitations that will be more difficult to overcome.

  • Lithium-ion batteries are a short-term energy storage solution.

  a.   When delivering power at full capacity, they provide around four hours of electricity. If lithium-ion batteries were to be used for long-term storage, it would require a large number of modules that would be impractically expensive and take up a large land area.

  b.   Hydrogen produced through electrolysis, while more expensive than lithium-ion batteries for short term power, becomes the more cost-effective option when produced in large quantities for long duration energy storage.

  • Demand for lithium may outpace supply

  a.   There is currently a global oversupply of lithium, which has helped to lower its cost. However, under the Paris Agreement targets for emissions reductions, the demand for lithium is projected to nearly double.[18]

  b.   The demand for lithium may grow even faster—potentially at an exponential rate—given the rapidly rising demand for electric vehicles and the development of the battery energy storage system industry.

  c.   This growth in the lithium-ion battery market may increase processing and production efficiency, but these gains could be offset by supply constraints that would increase prices for raw lithium.

  d.   To maintain reliable supplies of lithium and meet future demand, efforts are being made to diversify sources of lithium mining, which is highly concentrated in Australia and Chile, and to develop a lithium-ion battery recycling industry.

The projections for future lithium demand are based on current technologies. But as the demand for electric vehicles and energy storage systems increases, the research and development of alternative technologies will certainly attract more investment.

As these options become more commercially viable, the upward pressure on lithium demand could be reduced. In this scenario, lithium-ion production will continue to grow, but it would make up a smaller share of the overall battery market.

In consideration of these conclusions, there are some key questions that emerge about the future of lithium-ion batteries:

1.    In what specific needs and applications can lithium-ion batteries have the greatest and most efficient impact?

2.    What technologies could be more efficient and cost-effective in some of the applications for which lithium-ion batteries are currently used?

[1] https://www.iea.org/reports/energy-storage

[2] Samsung SDI, “The Four Components of a Li-ion Battery,” Technology, retrieved 31 January 2023, https://www.samsungsdi.com/column/technology/detail/55272.html?pageIndex=1&idx=55272&brdCode=001&listType=list&searchKeyword=.

[3] K Mongird et al., 2019, Energy Storage Technology and Cost Characterization Report, Pacific Northwest National Laboratory, 4.12.

[4] IEA, September 2022, “Electric Vehicles,” International Energy Agency, https://www.iea.org/reports/electric-vehicles.

[5] Robert Walton, 12 November 2021, “Global EV sales rise 80% in 2021 as automakers including Ford, GM commit to zero emission: BNEF,” Utility Dive, https://www.utilitydive.com/news/global-ev-sales-rise-80-in-2021-as-automakers-including-ford-gm-commit-t/609949/.

[6-10] IRENA, 2022, Renewable Power Generation Costs in 2021, International Renewable Energy Agency, Abu Dhabi.

[11,12] IEA, 2020, Projected Costs of Generating Electricity, International Energy Agency, Paris.

[13] Natural Resources Canada, 2022-03-10, “Lithium facts,” Government of Canada, Ottawa, https://www.nrcan.gc.ca/our-natural-resources/minerals-mining/minerals-metals-facts/lithium-facts/24009

[14] IEA, March 2022, The Role of Critical Minerals in Clean Energy Transitions, International Energy Agency, Paris, https://iea.blob.core.windows.net/assets/ffd2a83b-8c30-4e9d-980a-52b6d9a86fdc/TheRoleofCriticalMineralsinCleanEnergyTransitions.pdf, 10.

[15]International Energy Agency, (June 2019), The Future of Hydrogen: Seizing today’s opportunities, 43.

[16] K. Mongird et al., July 2019, Energy Storage Technology and Cost Characterization Report, Pacific Northwest National Laboratory, https://www.energy.gov/sites/prod/files/2019/07/f65/Storage%20Cost%20and%20Performance%20Characterization%20Report_Final.pdf.

[17] Energy Digital Magazine, 17 May 2020, “World’s Largest Flywheel Energy Storage System,” BizClik Media, https://energydigital.com/smart-energy/worlds-largest-flywheel-energy-storage-system

[18]International Energy Agency, The Role of Critical Minerals in Clean Energy Transitions, Revised version March 2022, https://iea.blob.core.windows.net/assets/ffd2a83b-8c30-4e9d-980a-52b6d9a86fdc/TheRoleofCriticalMineralsinCleanEnergyTransitions.pdf, 5.