Explained: Can Higher Energy Density Batteries Power Air Travel ?

One of the world’s largest battery manufacturers, CATL, has recently unveiled its new condensed battery boasting an impressive 500 Wh/kg energy density. The significance of this can be gauged from the fact that the firm teased the idea of electrifying passenger aircraft with its new battery revelation. And yes, it’s not yet another ‘demonstrator’ with no clear date on commercial manufacturing. The firm expects the technology to be ready for mass production this year itself. Notably, CATL is also making moves with its partners in developing electric passenger aircraft and practising aviation-level standards and testing by aviation-grade safety and quality requirements.

Let’s understand what makes energy density so important and what crucial role it plays.

What is Energy Density?

The energy density of a battery refers to the amount of energy that a battery can store per unit of its weight or volume. It is generally measured in watt-hours per kilogram (Wh/kg) or watt-hours per litre (Wh/L).

More the Energy Density, the Better

A higher energy density is desirable and means that a battery can store more energy in a given weight or volume. Higher energy density renders the battery more desirable for a plethora of applications, such as electric vehicles and portable electronics, where weight and space are important considerations. For an EV, more energy density allows the EV to travel further on a single charge. Additionally, an increased energy density would also make the EV more efficient, since it would require less energy to be charged and would be able to deliver more power to the motor, resulting in better acceleration and overall performance. And of course, carry less dead weight in batteries, giving designers more leeway to pack in features.

Generally, the energy density of a lithium-ion (Li-ion) battery ranges from around 260-270 Wh/kg. For instance, CATL’s Qilin batteries, which had recently entered full-scale production, promise up to 255 Wh/kg and are being integrated into EV models like the ZEEKR 009. Tesla’s in-house produced 4680-type battery cell gives 244Wh/kg, while Panasonic’s 2170 cells that Tesla uses in its long-range vehicles in the US come with 269 Wh/kg energy density. Now, CATL’s 500 Wh/kg battery comes with a bang, which will likely be a game changer in the all-electric range as it still awaits viable scaled production of long-promised solid-state batteries.

Search for a Higher Energy Density is Not New

Lithium-ion battery technology powers most of the batteries we use in autos today. But the issues with the Lithium supply chain have also been well documented. Thus, the demand for a longer range and increase in efficiency has led the scientific communities and researchers to try and develop more advanced battery technology for the sake of not just expanding battery use, including in new areas like air travel and make it greener but also for expanding the broader EV market. This has led to the development of several new promising battery technologies, that could augment or even replace Lithium ion batteries. Some of the frontrunners are as follows.

Solid State Battery

Solid-state batteries are known to be more efficient than lithium-ion batteries, as they can store more power within the same-size battery. This makes them a potential game-changer for electric vehicles (EVs) as they can help reduce battery size, charging time, and overall weight, which in turn can increase the range of the EVs.

Moreover, solid-state batteries have a longer lifespan and can be recharged up to seven times more during their lifetime compared to lithium-ion batteries. They’re also believed to be safer, because the solid electrolyte material is fireproof, unlike lithium-ion batteries, which are known to pose a fire risk.

While the technology is still in its early use, EVs may soon come powered by solid-state batteries. For instance, in 2023, the automaker BMW announced that it would begin testing solid-state batteries developed by Solid Power, a solid-state battery company, for use in its electric vehicles.

Scientists say solid-state batteries can have an energy density of about 350 Wh/kg. NASA took its battery technology to another level as it claimed to have achieved an energy density breakthrough with its solid-state battery hitting the whopping 500 Wh/kg energy density.

Lithium-Sulfur Battery

Lithium-sulfur (Li-S) batteries are a promising alternative to conventional lithium-ion (Li-ion) batteries for large-scale energy storage systems and electric vehicles. One major advantage of Li-S is its unprecedented energy density. With a theoretical capacity of up to 2,500 Wh/kg — significantly more than most Li-ion cells — it can store twice as much power in a single battery.

However, Li-S batteries currently suffer from poor longevity. Additionally, sulfur is affordable and abundant, which could mean lower costs. And since the manufacturing process for these batteries is like the one used for lithium-ion batteries, the same facilities could also be used for production.

EV battery manufacturer, Conamix, is working to make lithium-sulfur batteries a reality, aiming to have them commercially available within the next five years. Conamix also claims Li-S batteries require less energy to produce, reducing costs by over 25 per cent. One of the major drawbacks of this new battery technology is corrosion, though new designs are in the works to curb it. Another disadvantage is that these batteries in their current state don’t last nearly as long as lithium-ion batteries — about half the available charging cycles.

Metal-Air Batteries

Metal-air batteries use a metal anode and oxygen from the air as the cathode. These batteries can potentially achieve very high energy densities, as oxygen is abundant in the air and the metal anode can store a large amount of energy. Metal air battery has the advantages of good rate performance, high energy density, and low carbon sustainability. For instance, the energy density of lithium-air batteries measures about 12000 Wh/kg, significantly higher than lithium-ion batteries. Even the by-products are mainly metal oxides, which do not pollute the environment.

Some of the well-known metal-air batteries are Lithium-air, Aluminum-air, Zinc-air, Sodium-air batteries, etc. As per one research, the metal-air battery market size is anticipated to grow from USD 498 million in 2022 to USD 993 million by 2027, at a CAGR of 14.8 per cent from 2022 to 2027.

Growing demand for high-energy density storage solutions and the significant shift towards zinc-air batteries in electronic devices are some of the major factors propelling the growth of this market.

Currently, the metal-air battery has become the subject of intensive research worldwide and has made great strides in the past decade. Corrosion between electrolyte and anode in Zinc-Air batteries and rapid discharging of Aluminum- and Magnesium-Air batteries are among the reasons restricting the growth of metal-air batteries.

In Conclusion…

Battery energy density is one of the most important specifications that may be enhanced with technological advancements to help extend no-emission propulsion to the aviation sector. With a diverse spectrum of battery technologies being researched to increase the energy density of batteries, it may not be too distant to see the aviation sector getting powered by electricity. CATL’s 500 Wh/kg energy density battery is one such crucial development in the world of battery technology. However, there is still a long way to go before the dream of air travel becomes a reality.