Are solid-state batteries the holy grail for 2030?

Out of the transportation means which are powered by batteries, Lithium-Ion (Li-ion) constitute 95-99% of those batteries. Yet, the widely adopted rechargeable battery isn’t optimal for safety or resource-utilization.

Li-ion's massive uptake is in part due to Li-ion Nickel-Cobalt-Manganese (NCM) batteries, which have a good balance of energy density, power and comprise much of the present growth in battery electric vehicles in the automotive sector as well as for battery-hybrid and fully electric ships. From ships to tablets, NCM has had significant adoption in recent years, with manufacturers such as LG and Samsung putting it at the centre of their battery production portfolio.

Li-ion batteries have become winners because they are cheap and perform well. As the cost of these batteries has significantly reduced over the last decade, they are becoming a more viable alternative for long duration applications by simply stacking them in larger quantities. Today, these batteries have achieved low cost and increasing energy density - not by leap-frogging their competition with technological breakthroughs, but with simple and persistent engineering optimization of their production methods, tooling, speeds, and efficiency.

By extrapolating the present improvement rate, NCM Li-ion batteries will achieve $100/kWh at the cell level and will likely achieve 300 Wh/kg before 2030. Currently these rates appear linear, however if greater compounding occurs, these metrics will be met much earlier. For reference, within 10 years if the energy density of batteries is doubled, a vehicle such as the Tesla Model S won’t have 500 km of range, but 1000 km. Conversely, if the battery pack volume is cut in half, a Tesla Model S cost may be reduced as much as 50% because less battery is needed for the same performance, and the battery is the bulk of the vehicle cost. For a smaller vehicle like a Tesla Model 3 or Hyundai Kona EV, range could be doubled, or prices could be reduced 25-50%, indicating that a practical EV with long range could be purchased for a price in the range of 20,000-30,000 USD.

But the Li-ion batteries are also flawed. Present day Li-ion batteries use an electrolyte in which the main ingredient, by volume, is ethylene carbonate. The electrolyte is designed to lend stability to both the anode and cathode. Because ethylene carbonate is flammable, it contributes to concerns for battery fires and consequently toxic gassing. There are barriers for a greater use of existing batteries in transportation in addition to safety: cost; energy density (both volumetric- and weight-wise); charge- and discharge rates; and life-time.

Production of Li-ion batteries are also straining the world’s supply of cobalt. With over 55% of global reserves in the Democratic Republic of Congo, cobalt will face increasing constraints due to rising demands for both supply and connected to environmental and sustainability concerns associated with the mining process.

The question then arises whether there are any other battery chemistries that can both address these issues and compete with performance?

Not so solid ground for a change in dominant battery type

The co-founder of the Li-Ion battery, and recent Nobel prize laureate, John B. Goodenough, together with fellow researcher Maria Helena Braga, published a paper in 2017¹ on their development of a low-cost battery based upon a glass electrolyte that is non-combustible and has a long cycle life (battery life) with a high volumetric energy density and fast rates of charge and discharge: the solid-state battery.

A solid-state battery has the potential to improve most of the concerns with present-day Li-ion listed above. The glass solid-state battery can have three times higher energy density² by using an alkali-metal anode (lithium, sodium or potassium) that increases the energy density of a cathode and delivers a long cycle life. A solid-state electrolyte is presumed to be non-combustible or at least resistant to self-ignition. The non-combustible nature of solid-state batteries also reduces the risk of thermal runaway, allowing for a tighter packaging of the cells and consequently improving the design flexibility and volumetric density.

Further, Braga and Goodenough found that their solid-glass electrolytes could operate and maintain high conductivity at sub-zero temperatures down to -20C, addressing a major shortcoming of standard EV batteries.

Realizing these benefits can lead to a much wider use of batteries in transportation. Significant impact is especially expected in the heavy road transport and shipping industries. On the waterborne side, greater widespread of pure battery powered solutions in the ferry and short-sea segment is the likely first steps, with following greater use of hybrid applications in deep-sea shipping. The benefits of solid-state batteries, especially the safety aspects, can also expand the use of future aerial vehicles like drones for last-mile goods delivery³, urban air-mobility solutions⁴ and even larger passenger aircraft⁵. Additional benefits from an increased use of these batteries in transportation are increased energy conversion efficiency; less noise; reduced local emissions and GHG emissions, albeit if renewable energy sources are used. With all the benefits promised, many automotive Original Equipment Manufacturers (OEMs) have jumped on the solid-state bandwagon, acquiring stakes in battery manufacturers of this technology⁶.

However, solid-state batteries are currently on a low technology readiness level and basic research is still ongoing, with consequent uncertainties and concerns related to high production cost and scalability. The challenges in development are converting the insertion or deposition of the solid electrolytes to a process that is compatible with today’s manufacturing practices, all without affecting the durability or cost of the final product while adding benefits such as better energy & power density, increased safety, and higher throughput.

Some accounts claim that in the initial phase of development, solid-state technology is estimated to have high cost varying in the range of ~$800/kWh to ~$400kWh by the year 2026⁷. The comparatively high cost may significantly hinder production and uptake of solid-state batteries. However, with improved power density and lower cost, our Energy Transition Outlook forecasts that 50% of all new passenger vehicle sales in 2032 will be electric⁸. With a market breakthrough of solid-state batteries, it’s likely that these numbers will grow even further.

Despite its promises of performing for longer and without bursting into flames, the chances of solid-state taking over conventional Li-ion batteries number one spot will depend largely on a broad range of factors, from EV industry demand to overcoming initial costs.

Contributors

Main author: Hans Anton Tvete

Contributor: Davion Hill

Editor: Tiffany Hildre