Batteries: frequently asked questions

An introduction to batteries, from lithium-ion (Li-ion) and sodium-ion (Na-ion) technologies to battery raw materials including lithium, nickel, cobalt and manganese.

Batteries are critical to the energy transition. They power new electric vehicles (EVs) and provide energy support for grids with an increasing share of intermittent supply from renewables.

So, what are batteries made of? Are there different types? What are the benefits and challenges of increased battery use?

Read on for an overview, drawing on insight from our Electric Vehicle & Battery Supply Chain Service.

What is a battery?

Batteries are a form of electrochemical energy storage. They store energy through a combination of chemical reactions between materials contained in the battery. First invented over 200 years ago, batteries have since been made of many different materials, with different performance metrics.

However, all batteries have four common components: cathode, anode, electrolyte and separator.

How do batteries work?

In simple terms, chemical reactions at the anode release electrons and ions that flow to the cathode. The electrons flow through the external circuit (providing useful energy), while the ions flow through the electrolyte. At the cathode, a separate chemical reaction uses up the electrons and ions created at the anode.

The separator is an insulating material that prevents the anode and cathode (the electrodes) from touching. This prevents internal short circuits that would prevent the battery from powering devices.

Batteries come in two forms: primary and secondary.

  • In primary batteries, the reactions at the anode and cathode cannot be reversed, and so the battery is non-rechargeable. These include alkaline cells.
  • In secondary batteries, the electrode reactions are reversable. This means electrons are created at the cathode and flow to the anode during charging. Example secondary batteries include lead-acid and lithium-ion (Li-ion) batteries.

What are batteries made of?

Each battery is defined by what the electrodes are made of. Li-ion batteries, commercialised in the 1990s, quickly became the technology of choice for both EVs and energy storage systems (ESSs), each with different chemistry variants. Li-ion battery electrode materials react to provide/store energy through inserting, or intercalating, lithium ions (lithium atoms with a single electron removed). Since lithium is highly electropositive (easily gives up its electron) and has a small ion size, intercalation is highly reversible and batteries have a high energy density. This results in high capacity, high power batteries that can be charged and discharged many times – a high cycle life.

Anode and cathode materials are different from each other as the voltage of the battery is determined by the different electrode reactions. The more energy generated at the cathode, and the less at the anode, the higher the battery voltage. Anodes are typically made of graphite, while cathodes are either nickel-based or iron-based metal oxide compounds.

Nickel-based cathodes also contain other metals, including cobalt, manganese and aluminium. Iron-based cathodes can also contain some manganese.

The main cathode materials are:

  • Nickel-based: LiNixMnyCozO2 (NMC) and LiNixCoyAlzO2 (NCA)
  • Iron-based: LiFePO4 (LFP) and LiMnxFeyPO4 (LMFP)

Nickel-based cathodes tend to store more lithium per gram and litre of material and at a higher voltage. This results in a higher specific energy (Wh/kg) and energy density (Wh/L). Iron-based cathodes tend to be lower cost and have a longer cycle life.

For these reasons, nickel-based chemistries have been preferred for volume-limited EV applications while iron-based has been used for ESS applications, which benefits from a long lifetime.

Are Li-ion batteries the only option – what about sodium-ion?

Sodium-ion (Na-ion) batteries have received a lot of interest in recent years. A spike in prices of Li-ion battery raw materials, coinciding with technology development of Na-ion battery materials, meant Na-ion batteries could feasibly replace Li-ion batteries in some applications.

Like Li-ion batteries, Na-ion batteries come in many chemistry variants. However, these tend to use fewer, or even no, critical minerals. Na-ion batteries use hard carbon rather than graphite as the anode material, and some variants contain no lithium, nickel, cobalt or manganese in the cathode.

Switching to sodium does come with downsides. Because sodium ions are larger and heavier than lithium ions, more anode and cathode materials are needed to store the same amount of energy. Na-ion batteries are therefore heavier and larger than Li-ion.

For these reasons, we expect Na-ion batteries to be used in applications that have fewer constraints around volume or weight, such as ESSs, or in applications that don’t require as much energy storage, such as two- or three- wheeler electric vehicles.

What are the challenges associated with increased battery use?

The rapid adoption of EVs and ESSs as part of the energy transition doesn’t come without challenges. Lithium, cobalt, nickel and manganese are critical minerals, which have concentrated supply chains and are used in strategic applications.

Furthermore, battery raw materials usage has come under scrutiny over considerations of price, ESG metrics and carbon footprint, all of which differ by region and producer. This creates uncertainty in the battery outlook.

Indeed, it is a relatively difficult task for new companies to produce high quality materials, given the need to create electrode particles of certain shapes, sizes and composition with low impurities. Plus, scaling production of batteries – a complex manufacturing method – to meet the demands of the energy transition has created a highly competitive industry. The sector sees frequent technology improvements as companies look to maintain advantages, while integrating upstream to reduce vulnerability to volatile raw material costs.

Keep pace with changes in the EV and battery raw material industries 

To remain informed of the opportunities and challenges of such a complex and diverse industry, explore our Electric Vehicle and Battery Supply Chain Service. It provides a comprehensive solution for navigating evolving regulation, the EV outlook, automaker and cellmaker strategies, battery raw materials markets, the recycling sector and more.

Max Reid

Principal Analyst, Electric Vehicles & Battery Supply Chain Service