What is an EV solid-state battery?

01 August 2022

lithium-ion battery

Electric vehicles (EVs) currently rely on tried-and-tested lithium-ion technology. But solid-state batteries are the next big thing, as Phil Curry explains in Autovista24’s latest What is? video.

As the electric-vehicle (EV) market continues to grow, carmakers are constantly developing new technologies to improve their appeal and practicality to drivers. Solid-state batteries offer one of the biggest steps forward.

Current lithium-ion technology has helped to establish EVs in the automotive market. Yet questions remain about their viability for all drivers. Range and charging times are two issues that often cause debate over an EV’s practicality, while safety is also a problem, especially the potential of a battery fire.

Solid-state EV batteries could be answer to all these concerns. The technology is being developed by a number of carmakers, all of whom see it as the next step forward for the EV market. The build materials used in solid-state batteries have a big part to play in this progress.

The benefits of solid-state batteries

In a lithium-ion EV battery, the cathode (positive or oxidizing electrode) and anode (negative or reducing electrode) are made of carbon or graphite structures, separated by a polymer. A liquid, or gel, surrounds both structures, allowing ions to pass from one to the other.

However, the polymer substrate in a solid-state battery is replaced by a solid substrate, made of ceramic or glass. The anode structure is also replaced by a thin layer of lithium metal. The solid substrate allows for the movement of ions, meaning no liquids are required. This makes a solid-state battery smaller, lighter, and denser than a lithium-ion counterpart.

Therefore, carmakers are able to fit more solid-state units into the space where lithium-ion batteries would usually reside, increasing energy capacity and therefore EV range. If the manufacturer wants to keep this capacity the same, using fewer batteries would allow for a lighter vehicle, also helping increase the maximum travelling distance. In either case, weight is saved when using solid-state batteries, as this technology does not require as much cooling.

There is also a safety benefit. The liquids used in lithium-ion batteries are susceptible to heat or impact, and in a worst-case scenario, could ignite. With no liquids, solid-state batteries do not have this problem, and are therefore considered safer for use in EVs.

Currently under development

Carmakers that are developing solid-state battery technology include:

  • Toyota, which plans to launch a vehicle in 2025 using these batteries, possibly as part of a hybrid powertrain to begin with.
  • Ford and BMW, which have invested in Solid Power, a US-based solid-state specialist developing batteries for automotive use. ‘Solid-state battery technology is important to the future of electric vehicles, and that is why we are investing directly,’ commented Ted Miller, Ford’s manager of electrification subsystems and power-supply research. ‘By simplifying the design of solid-state versus lithium-ion batteries, we will be able to increase vehicle range, improve interior space and cargo volume, deliver lower costs and better value for customers and more efficiently integrate this kind of solid-state battery-cell technology into existing lithium-ion cell production processes.’
  • Renault, which is looking to find the best solid substrate for use as the conductive part of the battery construction. It is working with US startup Ionic Materials, which has already successfully developed a polymer that can conduct lithium ions at room temperature.

Autovista24’s What is? series explains some of the most important automotive terms and technologies used in the industry. Features on demand, semiconductorsover-the-air updates (OTA), bi-directional chargingelectric vehicles (EVs), type approvalautonomous technologyseasonally-adjusted annualised rate (SAAR), total cost of ownership (TCO), and residual values (RVs), have all featured so far.

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