What are the different types of electric vehicle batteries?
Batteries have become a part of our daily lives, powering the things we need to get through each day smoothly. These include TV remotes, smart gadgets, kitchen appliances, and even traditional combustion engines of vehicles.
Today, who would have thought that electric vehicle (EV) batteries would be developed that can make an entire car run!
EV batteries are in a state of evolution, resulting in the creation and constant improvement of various types of EV batteries. The research on battery manufacturing focuses on various areas, among them weight reduction of the battery, improved life cycle, recyclability, and energy loss reduction.
This article provides an overview of the different types of electric vehicle batteries that are available in the automotive market today.
What is an electric vehicle battery?
The EV battery is the most important part of an electric vehicle. It serves two main purposes: providing electricity to the motors that power the vehicle’s wheels; and storing energy during the overnight recharging via a standard electrical outlet.
EV batteries can also store additional energy. A vehicle generates kinetic energy during the slowing down process and when the driver steps on the brakes (“regenerative braking”). This excess kinetic energy ends up getting stored in the batteries.
What are the different types of EV batteries?
Over the decades and based on developing research, batteries of varying EV platforms have been phased out while others are being updated in terms of weight, functionality, and storage. There are also new battery types being developed with superior features to those currently available.
Before we get into the discussion of the types of electric vehicle batteries, how are EV batteries manufactured?
Contrary to popular belief, EV batteries do not constitute single cell units. They are battery packs consisting of individual EV battery cells that are assembled into battery modules.
Take the Tesla Model S Plaid as an example. The battery pack of the Tesla contains 7,920 lithium-ion 1865-type cylindrical cells. These EV battery cells are divided into five EV battery modules (each one containing 1,584 cells).
It must be mentioned that while these batteries vary in terms of their specific components, the way they work is practically the same: chemical energy is converted into electric power while the vehicle is running (discharging) and then electric power is converted back into chemical energy for storage (charging).
Below are the five types of EV batteries:
- Lead-acid
This is the oldest type of rechargeable battery. In this battery, lead electrodes are submerged in a sulfuric acid solution. Lead-acid batteries are the cheapest, easy to replace, and are low maintenance in comparison with other EV batteries.
However, they are not environmentally friendly because of the gasses they produce. They are also heavy and have a tendency to lose capacity fast. - Lithium-ion
This type is most commonly seen in today’s EVs. Here, both the anode (negative electrode) and the cathode (positive electrode) contain lithium ions.
The electrodes are bathed in a liquid electrolyte, a lithium salt solution (lithium hexafluorophosphate). There is a separator – carbon coated copper foil or original thickness aluminum foil – between the electrodes.
When the vehicle is discharging, the anode transfers positively charged lithium ions to the cathode via the electrolyte through the separator. This movement of ions generates electricity.
Among the features that make lithium-ion EV batteries the best for electric cars are its high energy efficiency, efficient performance in high temperatures, high power-to-weight ratio, low energy self-discharge, and potential for sustainability. Their main disadvantage is its high cost of mass production. Present research is being done on an alternative lithium-ion polymer battery which is cheaper to manufacture. At the end of a battery’s life cycle, they may either be refurbished for use in less demanding applications or undergo “destructive dismantling”. - Nickel-cadmium
This EV battery differs from lithium-ion in that they utilize cadmium in the anode and nickel oxide in the cathode. Its mechanism of action is the same as lithium-ion batteries.
During discharging, the resulting chemical reaction between nickel hydroxide and cadmium hydroxide in a potassium hydroxide electrolyte solution produces electricity. A similar chemical reaction occurs during charging which sees the anode transforming into cadmium. It is this transformation back into cadmium – a known carcinogenic – which has prompted the phase out of this type of battery. - Nickel-metal hydride
Similar to nickel-cadmium batteries, nickel-metal hydride has a longer life cycle and good storage density. Here, the anode is a hydrogen absorbing alloy while the cathode is nickel oxy-hydroxide.
Among its advantages is that it utilizes an electrolyte aqueous potassium hydroxide with a lithium hydroxide additive. This electrolyte improves the cathode charging efficiency through oxygen evolution reduction. Presently, studies are underway regarding sustainable energy promises being offered by hydrogen-based batteries, like nickel-metal hydride batteries. - Solid-state
Although still considered in the experimental phase, solid-state batteries have generated interest in the automotive industry. Unlike the other battery types which utilize liquid or non-aqueous electrolyte solutions, solid-state batteries contain solid materials in the form of plastic polymers, compacted inorganic powders, ceramic, or glass.
These have greater stability, energy density, and temperature control. While they are currently very expensive, researchers are hoping to lower costs by the time they are introduced in the year 2030.
What is the capacity of electric car batteries?
Capacity is defined as the amount of energy that is stored in the EV battery cells of a battery pack. It is measured in kilowatt hours (kWh). Presently, the components found in lithium-ion batteries make them the best batteries to date because of their larger storage capacity.
In general, the average capacity of EV batteries is between 20 kWh and 100 kWh.
Wrap Up
While these types of EV batteries are far from perfect, scientists are making headway in developing ones that are more energy efficient, lightweight, and cheaper to mass produce. It is hoped that new EV batteries, such as the highly anticipated solid-state batteries, can provide improved features and greater mileage for EV owners.
