Understanding EV Battery Technology
Despite the economic fall-out of the pandemic, 2020 saw global electric vehicle stock hit the 10-million mark, an 43% increase over the previous year. Two-thirds of these are battery electric vehicles. In the Netherlands, BEVs account for 82% of all-electric car registrations.
Engineers are determined to make EVs more accessible, and to that, they need to be more affordable. Affordability starts with the battery technology that powers these vehicles.
Trends in EV Battery Technology
While electric vehicles have been around since the 1800s, EVs only re-entered the collective consciousness in the late 2000s with the production of Tesla’s Roadster. The roadster was the first car to feature lithium-ion batteries in a production car while demonstrating a 200-mile driving range.
Today, virtually every automaker has an EV or hybrid electric vehicle on offer in a bid to become the first mainstream company to launch affordable electric cars that can perform as well (or outperform) fossil-fuel-powered vehicles on the road.
Their success or failure will usually boil down to a review of their battery technology – specifically recharge speeds and range. This technology is exceedingly complex and will require a giant leap in battery technology. Specifically, researchers are focusing on a move to solid-state batteries.
Image: EVs reached the 10-million mark in 2020
How EV Batteries Work
In the most elementary terms, batteries are charged when electricity flows from its negative electrode (anode) to its positive electrode (cathode) via electrolytes. When a battery is in use, the flow goes from the anode to the cathode.
In electric vehicles, the flow between the positive and the negative electrode is made through positively charged lithium-ions. An EV battery may contain either graphite or silicon anode, lithium metal oxide cathodes, and a liquid electrolyte.
As most EV aficionados know, these lithium-ion batteries can only store a relatively low amount of energy. In practical terms, this means that an electric car can only drive so far without requiring a charge.
The earlier models in the 2010s could only travel about 100 miles without recharging, while top-of-the-range modern equivalents like the Telsa S can reach 300-400 miles on a full charge. Most EVs have a real-world range of about 250 miles.
This performance can vary depending on the size of the battery, whether you used a rapid charge or an overnight charge, how full the car is, how many accessories it has, and of course, your speed.
Liquid State Lithium-ion Batteries
Most electric vehicles use lithium-ion cells in their batteries, and researchers actively focus their attention on improving them. Thousands of new patents related to lithium-ion batteries are filed every year.
New materials that have been used in the creation of batteries include nickel manganese cobalt oxide (NMC) and nickel cobalt aluminum oxide (NCA). NCA was commercially used in lithium-ion cells for Tesla’s Model 3 (2017). It offered a high-energy-density battery at over 700 watt-hours per liter.
Unfortunately, the use of cobalt is controversial. 65% of cobalt deposits are mined in the Democratic Republic of Congo, a country plagued by reports of human rights violations, child labor, and environmental negligence. The price of cobalt has also considerably risen over the last few years.
As a result, Tesla announced in 2020 that they would eliminate the use of cobalt in its batteries and focus on alternatives, including lithium iron phosphate. With a lower energy density and a lower weight, it should extend the battery life, and subsequently, the EV range.
When working with lithium as an anode material, there are issues, including the shedding of lithium ions due to the expansion and shrinking of the anode volume during the charging/discharging process. The shedding or build-up is called lithium dendrite and can lead to short-circuiting and, ironically, a shorter battery life.
Lithium-Based Solid-State Batteries
Researchers believe that solid-state lithium batteries will remove the problems experienced with liquid electrolytes, with the added benefit of making batteries smaller.
Solid-state batteries will use a solid electrolyte instead of the liquid or polymer gel most commonly used. It can take the form of ceramic, sulfites, or solid polymers.
The battery works the same as described before. When delivering power (discharging), the positively charged ions travel from the anode to the cathode. Because the electrons can’t travel through the electrolyte, they travel across a circuit and deliver power to whatever it’s connected to, e.g., an electric motor. During charging, the electrons are pulled to the anode across a circuit from the cathode. When no more ions flow to the anode, the battery is fully charged.
Image: Lithium-ion battery advancement may lead to a revolution for EVs
There are many solid-state batteries existing, primarily used in small electronic devices like pacemakers. Most are not rechargeable. But they have potentially up to ten times the energy density of liquid-state lithium-ion batteries of the same size.
Solid-state batteries will be more efficient and require fewer cooling and control components. As a result, they will weigh less.
If successful, EVs will become more powerful, more compact, with a more extended range and faster recharging. Some researchers believe that solid-state batteries could be recharged up to seven times more, giving them a much longer lifespan than the current lithium-ion battery.
While recent developments in these solid-state batteries have been exciting, the technology has a long way to go. Finding the suitable material from which to make the electrolyte has been a significant challenge. Thinner electrodes are required, which has a low margin for error during manufacturing, especially at scale.
Alternatives to Lithium-Ion
Other EV manufacturers are looking beyond lithium-ion batteries altogether. Some alternatives may include:
Hydrogen Fuel Cells
Toyota is one of the manufacturers hedging their bets on hydrogen fuel cells. In terms of its production, byproducts, and recycling, it’s cleaner than lithium. Unfortunately, its production still depends on fossil fuels. A lot of work is being done to produce hydrogen at scale from renewable sources, also called green hydrogen.
Graphene Supercapacitors
Graphene supercapacitors have been bandied around as a solution to the world’s energy problems for a decade. Unfortunately, we haven’t cracked the technology yet. Supercapacitors charge and discharge more efficiently than batteries do. If we can produce them from graphene, we’ll get energy density through weight saving and compact packaging.
Redox Flow Batteries
These dual-liquid batteries use hydrochloric, and sulfuric acid and have a 70% higher energy density than a lithium-ion battery. In theory, they could propel a car up to a thousand miles on a single charge, but we haven’t seen any real-world prototypes yet.
Aluminum-Graphite Batteries
Stanford University developed these batteries that could theoretically charge a car in minutes. Unfortunately, the current output of 1.5v can’t charge a phone, much less a car, but if it works, it could provide a fantastic, lightweight, safe battery for electric vehicles.
Solar Panels
Elon Musk has worked on a solar roof in the past, and there have been several solar prototype vehicles released in history. Solar panels aren’t particularly efficient at present but, as they get better, we may see cars that harness the sun's power soon.
Powered Roads
Some scientists are thinking outside the box, looking at roads that can power cars. In Sweden, trucks hook into overhead power lines, while the Netherlands has a solar road that can supply power to lights in the area. While it would require a mass investment in infrastructure and maintenance, it’s worth examining all the alternatives.
Bioelectrochemical Batteries
Researchers are looking to anaerobic bacteria as a source of power. They process acetate with an oxidation method that releases electrons. Researchers in the Netherlands have created a promising prototype that managed to get through fifteen cycles, which unfortunately means it's far from viable.
Theoretically, bacteria could reproduce and result in a battery with an infinite lifespan, but it’s still closer to science fiction than reality at present.
Producing Better Batteries at Scale
The success and future of electric vehicles depend on our ability to develop batteries that charge more efficiently, stores energy for longer. They outperform fossil cars without costing an excessive amount.
Developments in current lithium-ion batteries could very well lead to the breakthrough we need to take a quantum leap with electric vehicles. Omar Morales is the Director of Operations and Project Management for Advano, which has made dramatic strides in bringing lithium-ion batteries into mainstream manufacturing.
The company produces silicon nanoparticles by the ton from silicon wafer scraps that are ground down to produce battery anodes at a low cost.
This not only resolves battery efficiency issues but provides companies with the ability to mass-produce lithium-ion batteries. The economies of scale mean that EV batteries – and EV themselves – can become more affordable.
To find out more, visit the Advano website. To learn more about engineering project management check out the Omar Project.