With the steady rise in popularity of electric vehicles (EVs), the quest for developing more sustainable batteries and charging points has become all the more important.

Currently, the most popular type of EV battery is a lithium-ion model, which contains a plethora of rare and difficult to source materials, including cobalt, manganese, and even the lithium itself. Additionally, the mining process poses many threats to both the people involved and the surrounding ecological landscape.

It’s no surprise, then, that one of the most popular fields of research in the development of electric vehicles is how we can find ways to create stronger, more sustainable batteries that use more abundantly available materials such as sodium or hydrogen.

So, let’s take a quick look into the history of electric vehicles and their batteries, learn more about how they work, and then see what the future holds for battery technology.

A brief history of electric vehicles

Our understanding of electric cars and battery packs is still relatively new, but we have already made great progress in development since the first commercial, mass produced electric cars hit the market in the late 1990s. But that’s not to say that research hadn’t been conducted before this point.

In fact, the first recognised electric cars were developed back in the 1880s, first in 1884 by Thomas Parker, an English inventor who also worked extensively on the electrification of the London Underground, then again in 1888 by German engineer Andreas Flocken. This latter invention, the ‘Flocken Elektrowagen’, is widely considered to be the first real, practical application of an electric car.

Then, by the 1890s, William Morrison pioneered electric car development in the United States by engineering a vehicle capable of transporting 6 people at speeds of 14 miles per hour.

To do so, he modified and advanced the existing lead batteries by:

• making them lighter

• adding glass-wool insulation to prolong the battery’s life and lessen the chance of it short-circuiting

• preventing the lead plates from shedding material

• increasing the overall power output

The car apparently needed 24 batteries in order to achieve its maximum speed. In the mid 1890s, Morrison sold his patent for this battery to the American Battery Company for $21,000. In today’s money, that’s around $700,000.

How do electric car batteries work?

The main principle and function of a battery remains the same, no matter what shape it takes.

The basics of a battery include three essential components:

• an anode: a positively charged electrode

• a cathode: a negatively charged electrode

• electrolytes: the solution component that transfers ions (charge-carrying particles) between the anode and the cathode

In a battery, the anode reacts with the electrolyte which causes electrons (which have a negative charge) to build up within the anode. This creates an electrical imbalance between the electrodes.

Through a process of oxidation and reduction, the electrons travel through an external path (oxidation) to the cathode (reduction). This creates an electric current which provides a charge to whatever the battery is connected to. When a battery is recharging, the flow of electrons is reversed.

During this process, positively charged ions travel through the electrolyte separator to help maintain a neutral charge balance at the electrode for stability.

In an electric car, a battery will be made of thousands of cells. These can be cylindrical, prismatic, or pouch shaped. A lithium-ion battery (the most common battery type found in modern electric cars such as the Tesla model S or the Nissan Leaf) contains:

• a cathode made of nickel, manganese, and cobalt

• an anode made of graphite

• an electrolyte made of lithium-ions

Types of electric vehicle batteries currently available

Now that we have a better understanding of how batteries work, let’s look at some of the most popular batteries currently used in EVs across the globe.

Lithium-ion batteries

Lithium-ion batteries (LIBs) are the most common type of battery cells, found in the vast majority of electric consumer goods such as smartphones, laptops, and electric toothbrushes, to name a few.

There are a number of benefits to using LIBs:

• LIBs are quick to charge and can last a relatively long time due to their high energy density.

• They are generally smaller and more lightweight than their counterparts with a good weight-to-power ratio.

• They have a slow self-discharge rate.

However, despite being hugely popular, they don’t come without their risks.

• LIBs are expensive to produce due to the cocktail of relatively rare materials they use. Not only that, but the way in which these materials are sourced is incredibly unethical. For example, this report by the New York Times looked at the exploitation of workers - many of whom are children - in the Democratic Republic of Congo, where the majority of the cobalt LIBs use is mined. The problem is so severe that cobalt has been dubbed “the blood diamond of batteries”.

• LIBs are one of the most flammable battery types, as they are very sensitive to heat and the electrolytes have a tendency to release flammable gases if over-exerted. This means they often require additional protection from high voltages and temperatures. Once this is counteracted, however, they are exceptionally better than other modules.

Nickel-metal hydride batteries

Nickel-metal hydride batteries (NMHBs) are mainly used in hybrid-electric vehicles (HEVs), such as the Toyota RAV4 EVs, as they are recharged using fuel rather than an external charger.

HEVs work via a collaboration between a normal combustion engine and electric motors. Dual power means that the electric motor can power the car when slow driving is required, making it perfect for travelling in towns and cities. Then, when a car needs more power, the system can switch to its regular combustion engine. The kinetic energy produced from braking and driving is then used to power the battery back up.

Despite having a longer life-cycle and being more environmentally friendly, NMHBs have, for the most part, been replaced in HEVs as well by lithium batteries, as they:

• have a high cost

• have a high self-discharge rate

• generate a lot of heat

Lead-acid Batteries

Lead-acid batteries (LABs) are the main battery type found in petrol and diesel cars, but they can occasionally be found in EVs as well to supplement an additional battery type. They can be found in older EVs, such as the Ford Ranger EV.

The advantages of LABs are that they:

• are inexpensive compared to other batteries

• have a high power threshold

• are reliable, durable and well-researched

Nevertheless, they are one of the heaviest forms of car battery, and come with a host of problems including:

• susceptibility to extreme temperatures

• charging issues when worn down

• a shorter life-cycle

• the possibility of an acid leak and explosion

Types of EV batteries in development

Every day, plans for new battery types are being developed in an effort to achieve greater sustainability. Let’s have a look at some promising prototypes we may see on the roads very soon.

Sodium-ion batteries

Recently, sodium-ion batteries have been rearing their heads in China, via companies such as Jiangling Motors Electric Vehicle (owned in part by Renault).

Sodium is a more reactive element than lithium, but found more abundantly all over the world. It forms the basis of salt and sodium carbonate, also known as soda ash, huge deposits of which can be found across the US. This is a key component in the development of sodium-ion batteries.

Immediate advantages of using sodium over lithium are that:

• sodium as a raw material is cheaper to mine, and costs significantly less per tonne ($230 USD vs $37,000 USD)

• it is safer to use

• it is more sustainable as there is more of it

• they are extremely resistant to cold temperatures

However, drawbacks include:

• Due to a lower energy density, more sodium is needed to equal the power provided by lithium batteries. But, recent developments by the company HiNa Battery in China is helping boost the capabilities of sodium-ion batteries, and has begun mass production for both vehicles and home energy storage.

• Whilst soda ash is readily available in the US, China have resorted to using coal fuelled plants to produce synthetic soda ash, which instantly mitigates the environmental benefits of using sodium in the first place.

Solid-state battery

In a solid-state battery, the electrolyte layer, usually a liquid, is made of solid materials such as silicon or lithium metal. Currently, solid-state batteries are looking like a very promising alternative to counteract many issues faced by existing EV battery packs.

• A solid electrolyte reduces the risk of thermal runaway, which is where the material of your electrode reacts negatively with your electrolyte and leads to a chain reaction of thermal events which eventually cause a fire

• Solid electrolytes increase the energy density, which gives a greater battery capacity

• Batteries which use solid-glass electrolytes can resist sub-zero temperatures

Nevertheless, extensive tests are still being conducted, and automakers have not yet incorporated solid-state batteries into EVs beyond prototypes.

How can we be more sustainable?

The International Energy Agency predicts that, by 2030, over 300 million EVs will be driving around across the globe. It’s unreasonable to suggest that battery manufacturers should develop millions of individual batteries for each vehicle, which will ultimately cause a huge strain on critical minerals required for their development.

Rather, we should be focusing our efforts on battery recycling, and giving existing EV cars a second life rather than writing them off for scrap. This is something Tesla aims to do with 100% of their batteries.

There are many points within the battery supply chain where it is possible to reuse components, and end-of-life packs don’t automatically have to go to landfills.

There are three key ways this can be achieved.

1. Pyro-recycling: smelting existing batteries allows manufacturers to recover various metals and minerals which can be refined and used again

2. Hydro-recycling: hydrometallurgy helps recover minerals from ‘black mass’, which is a fine powder that forms when batteries are crushed or shredded. With hydrometallurgy, metals from the black mass are dissolved and separated with solvents or precipitation to be collected and reused.

3. Direct recycling: this process breaks down a battery in full and separates out the useful, usable sections so all active parts can be recycled.

So what comes next?

There’s still so much that can be done to improve EV batteries and develop more sustainable storage. One important way is via making more use of renewable energy to charge batteries in the first place, as well as using more sustainable practices to reduce emissions that come from manufacturing factories.

Hopefully the government will increase incentives to encourage the development of better, more environmentally friendly practices - ones which will apply to both carmakers and consumers alike. Ultimately, the goal is to create a greener, better world. That’s something everyone can agree on.