Toyota Is Releasing a Solid State Battery EV. Will Tesla Follow?
What is a Solid-State Battery and Why it May Change EV’s Forever
Current EV battery technology has a number of deficiencies that make it not ideal for long-range electric vehicles. Advances in battery technology have increased the range and power of EVs, but none come close to matching the convenience, cost, and range of a petrol car. However, there is hope. Solid state battery technology offers a better solution. Whilst not suitable for all applications, this new technology may herald improved ranges for EVs or even the creation of an entirely new vehicle category.
What is a solid state battery?
A solid state battery is a rechargeable battery in which the electrolyte is in the solid state rather than the liquid or gaseous state. This means that they have very high energy density, can be discharged and charged rapidly and have no flammable components.
How do they work?
Basic batteries contain two electrodes — an anode and a cathode separated by an electrolyte. When charging or discharging electrons are exchanged between these two electrodes, creating current flow.
The electrolyte conducts negative ions (cations) from the cathode to the anode as electricity is produced, keeping them separate at other times. The two electrodes are bound together by another material called a separator.
In a solid state battery, this liquid electrolyte is replaced by a solid material. These materials have high conductivity and are unable to evaporate in the same way that liquid electrolytes do. This means that the risk of thermal runaway is greatly reduced and the batteries can be used at higher temperatures.
What makes them superior to traditional lithium-ion batteries?
Solid state batteries have advantages over existing battery technology in four key areas: safety, charge speed, range of travel and energy density.
Safety
Solid state batteries are safer than traditional liquid electrolyte batteries due to the lack of flammable electrolytes. Because the electrolyte is a solid, there is no risk of ignition that can lead to thermal runaway. The solid materials do not evaporate as they charge and discharge, so there is no risk of exothermic reaction during charging. Thermal runaway typically occurs when a battery overheats, usually due to overcharging or damage caused during charging or operation.
Charge speed
Another problem with traditional li-ion batteries is that they can be difficult to charge quickly. When a battery is full it takes time to slow down the flow of ions and when a battery is empty it takes time for current to build up. This makes charging time unpredictable and unattractive for vehicle applications.
The solid state battery, however, can be charged up to 80% charge in just fifteen minutes. Comparatively, existing batteries only charge up to 50% in fifteen minutes.
Range
Solid state batteries can be charged and discharged many times more than traditional lithium ion batteries without strain. This makes them ideal for longer range electric vehicles which make up the majority of the market. Currently, a loss of capacity after 1000 cycles is typical for li-ion batteries, whereas solid state batteries retain 90% of their original capacity after 5000 cycles.
Energy Density
The energy density of a battery is the amount of energy it can store per unit weight. The higher the density, the more energy an EV can store.
The use of solid electrolytes means that these batteries contain an electrode in liquid form thereby increasing their energy density compared to traditional batteries.
The graph below illustrates that lithium-ion batteries have poor energy density when compared to other battery technologies, especially solid state ones.
What about the rest of the vehicle?
Currently, long-range EVs need large, heavy battery packs to achieve their range. With lighter, cheaper and more powerful solid state batteries on board, the weight savings are substantial. The size can also be reduced by two thirds with these new cells compared to lithium-ion technology at a comparable price point.
These factors combined mean that solid state batteries will offer an unrivalled user experience for long-range electric vehicles.
Why aren’t solid state batteries used in today’s EV’s?
Solid state battery research is still in its infancy. Solid state technology is not suitable for certain applications and it needs further development to make it viable on a large scale. As such, it will be some time before these technologies can prove that it can compete with lithium-ion batteries on price, real world usability, scale, durability and infrastructure.
Cost
The cost will have to come down if solid state technology is going to be applicable for mass market EVs. At present they cost 3 times more per kW than li-ion batteries, but the costs of the materials used in li-ion cell make up just 20% of the overall cost. More research into cheaper materials will reduce the price and make this technology viable for the mass market.
Real-world usability
Although solid state batteries have similar performance to lithium ion batteries when tested in the lab, it is harder to achieve this rapid charge in real-world conditions. The quick charge times in lab tests are only possible using lab-grade materials and charging equipment which are far too expensive for use in EVs.
Scale
Solid state batteries are still in the development stages and have not yet to be produced on a large scale. However, there is plenty of interest from automotive companies, universities and start-ups pioneering solid state battery production. The Netherlands announced in May 2017 that over €900 million will be invested into solid state batteries as part of their Energy Innovation Agenda.
Durability
There have been no tests by third parties on the long-term use of solid state batteries to compare them with traditional li-ion batteries. This makes it hard to say for certain whether they will last longer than traditional li-ion cells in an EV, which need to last 10 years or more. A solid state battery for a car is only as good as the rest of the components around it. Ensuring all components are compatible and there are no issues such as hot-spotting in the cells or degradation in performance over time will be crucial to keep EVs running smoothly for many years to come.
Recharging infrastructure
Recharging stations need to be able to handle a much faster charge than traditional li-ion batteries. Charging stations with equipment that cannot cope with the new technology may not be compatible with solid state batteries at full speed and could cause thermal runaway. The charging technology would also need to be up to the job of handling the very large charging power that solid state batteries have the potential to achieve.
Toyota’s Investment into Solid State Batteries
With all of these potential drawbacks in mind, it’s great to see a large amount of investment and R&D in this area. Recently, Toyota announced a prototype car using solid state batteries that will be announced this year. Given that they own more than 1000 patents on solid state batteries, and that Japan created a $19b green fund which includes investments in solid state technology, it’s not surprising to see them lead the way.
So while solid state batteries may not be ready for widespread EV use just yet, investors in this important area of future transport technology are worth watching. The technology has the potential to shake up the EV industry and create another technological breakthrough which improves the lives of people around the world.
Will Tesla Follow?
With all this going on, it’s surprising that Tesla is not actively developing the technology. It would certainly fit in well with their ‘Master Plan’. However, lots of their patents are around battery charging and charging infrastructure which suggests they are well aware of the potential of solid state batteries and may just be waiting for the technology to mature a bit more before making a move.
In summary
In summary, solid state batteries could be the ideal technology to help deliver a long range electric vehicle that is affordable, realistic and truly enjoyable for all consumers. However, it still has some way to go before it can be implemented on a large scale. Costs will have to come down, the technology needs to be tested in real world conditions and the infrastructure needs to be improved. As always, one step at a time.
With so much money being invested into this new technology, it is likely that it will become a reality within the next few years. Therefore, it is only a matter of time before more research takes place and solid state battery prices fall further as production increases. Then this new technology may well find its way into your EV very soon!
