Between the demand for lithium-ion in small device batteries and its usage in EV energy storage, it is becoming apparent that this type of battery technology is not the optimal long-term energy storage solution.
According to the last Global EV Outlook, the number of EVs on the grid could reach as many as 20m units by 2020 and at least double again to 40m by 2025, yet the leading energy storage solution is based on a limited resource with debatable performance levels.
The questions manufacturers should be asking are, what are the less expendable alternatives, how does their performance capability differ, and are they market-ready?
For any new technology, especially related to vehicles, safety, cost, performance and sustainability are the key concerns of any forward-thinking manufacturer.
Manufacturers should also consider other use cases for the technology in the grid to encourage and enable wide-scale adoption.
We explore the newest developments in EV energy storage to find out more about how the industry can best facilitate the growth of the EV market.
1] Solid-state batteries
Perhaps the best documented alternative to lithium-ion batteries are solid-state. Many manufacturers of EVs, including Honda, Hyundai, Nissan, BMW and Toyota, have begun to explore the technology.
The rush is now on for manufacturers to pip to the post, with companies such as Toyota and Hyundai announcing 2020 market release, trumping Fisker Automotive’s prior promise of a 2023 solid-state battery release.
As well as having higher capacity, the technology is more sustainable than lithium-ion batteries. They need less manganese, nickel, cobalt, aluminium and lithium, making the batteries more compact and thus more commercially viable in the automaking industry. Other potentials include faster recharge time and a longer life cycle.
Additionally, solid-state battery cells do not need to be layered closely together and linked by electric connectors, meaning that manufacturers and designers have more flexibility when laying out the cars’ structure.
In theory, solid-state battery technology will also be far safer, bypassing risk of leakage or volatility found in liquid or gel-based lithium-ion batteries.
Even Elon Musk flagged in 2011 that supercapacitors, not batteries, would likely power future vehicles.
Supercapacitors, or electrochemical double layer capacitors, have a much higher power density than batteries, potentially making them more efficient in the delivery and absorption of energy.
This would have a particularly significant benefit in the use case of EVs as they would be able to charge in minutes as opposed to hours. The drawback for EVs is that supercapacitors can’t hold the same amount of energy as current battery technologies.
The trade-off between supercapacitors and lithium-ion batteries for charge time and journey distance has been widely discussed across the industry, with some believing consumers would rather have the quick charging capabilities of supercapacitors over the range of lithium-ion batteries.
Additionally, supercapacitors have demonstrated a seemingly infinite resilience when charging, versus lithium-ion batteries that lose the ability to charge over time.
3] Graphene fuel cells
Although not yet as advanced or widely applicable as other EV storage technologies, graphene fuel cells offer a renewable alternative with huge potential.
According to the US Department of Energy, there are still many challenges for stationary and portable fuel cells. Much like with supercapacitors, graphene fuel cells have low energy storage density, however, they can offer unparalleled energy per mass levels, thanks to hydrogen conduction.
Thanks to the size of graphene - only one atom thick - the layer will allow only the smallest molecules to pass through, acting as a shield between the fuel cell nanocrystals and external contaminants.
Typically, graphene is difficult to create perfectly, however these natural imperfections are desirable for shielding fuel cells. The natural holes allow smaller hydrogen molecules to pass through, overcoming the degradation and performance issues.
The technology is, however, far from ready for transport application, with the Graphene Flagship predicting readiness post-2028.
There are two key issues facing the use of graphene fuel cells in the transportation market. A large concern for many is the associated degradation issues that are currently not well understood. Poisoning and coking in proton exchange membrane fuel cells increases the risk of the technology, making them less than ideal for transport.
Secondly, the cost for production and retail of graphene fuel cells would not be competitive for the EV market, as fuel cells require a noble metal as a catalyst.
Bi-directional vehicle to everything (V2X) charging enables electricity to be transmitted between an on-board battery and infrastructure, discharging excess electricity stored in EVs and plug-in hybrid electric vehicles (PHEVs) back into the building or grid.
One recent project demonstrating the commercial viability of this solution comes from Hitachi Europe, Mitsubishi Motors and ENGIE, using EVs as a means of energy storage for an office building. To do so, the consortium linked Hitachi’s V2X charger to ENGIE's office building in Zaandam.
Not only can the charger recharge EVs and buildings or grids, but operators can also connect solar panels and external storage, allowing a much more efficient electricity supply to both buildings and EVs.
According to a statement from Mitsubishi: “The V2X Charger is connected to the building's energy supply and, when the building generates more solar power than it needs, this excess energy is stored in the battery of the electric car. This energy can then be discharged back into the grid when appropriate. The car battery therefore acts as an energy storage source, as well as an emergency power supply.”
Vincent Cobee, Corporate Vice President at Mitsubishi Motors, believes bi-directional EV charging is a crucial component of future smart cities, saying, "this demonstration will help to provide a new energy solution for energy efficient, low carbon smart buildings. We are aiming to show that EVs and PHEVs can be a vital component of urban energy in the future. "
Such advances as these will undoubtedly come together to form a picture of the future EV market, as well as wider technology. With so many new opportunities for energy storage entering the market, the industry is geared for an exciting few years of development and growth.
For more insight into the EV market and upcoming informational events, tune in to our Engerati webinar, ‘Balancing the grid: innovative charging and storage solutions to support widespread EV adoption’