How will carbon-ion cells shape our future?By our Editorial Team - 1st February 2018
Stephen Voller, Founder and CEO of Zap&Go, explains how carbon-ion cells are shaping the future of energy storage for consumer electronics and automotives.
Lithium-ion batteries are widely used in consumer electronics and automotive because they have a high energy density. However, they contain highly flammable electrolytes that can become unsafe if overcharged. While work is ongoing to address this, another solution presents itself in the form of supercapacitors, which store and deliver electrical energy at ‘super’ speeds.
Currently, commercially-available supercapacitors are made using activated carbon with an organic electrolyte – due to the electrolytes, they remain flammable. About 6 years ago, however, researchers at Oxford University developed a cell that uses nanocarbons and ionic electrolytes. The cell works safely at higher voltages, which offers increased energy density.
Stephen Voller is a recognised authority on energy storage devices, having co-founded the hydrogen storage company Cella Energy, launched the first ever CE-marked hydrogen fuel cell product, and most recently (in 2013) founded ZapGo to produce carbon-ion cell technology, based on that developed by Oxford University a few years back. We spoke to Mr Voller about the technology underlying 'C-Ion' cells, and the potential for these cells to shape the future of consumer electronics and in the automotive industry. (C-Ion is a registered trademark of Zap&Go.)
As an overall introduction, can you summarize the advantages of C-Ion cells versus lithium-ion batteries?
Although it is currently the industry standard for rechargeable batteries, Li-ion works by an electrochemical reaction, raising the risk of fires in consumer products. Also, Li-ion batteries can take hours to recharge fully, and they are limited to about 1,000 charge-recharge cycles before they begin to wear out. These drawbacks formed the impetus for a new rechargeable technology that does not involve a chemical reaction or the risk of fire, can be recharged up to 100,000 times without wearing out, and can be recharged in a matter of minutes rather than hours.
As such, ZapGo has developed carbon-ion (C-Ion) technology, a faster-charging, environmentally friendly, safer alternative to rechargeable batteries. C-iIon is being used today in a range of products, including cordless power tools and autonomous electric vehicles, combining the capacity and slow discharge performance of Li-ion batteries with the time to charge, safety and environmentally friendly features of supercapacitors.
How do cells like these deliver energy at ‘super’ speed?
ZapGo’s C-Ion cell incorporates patented advanced nano-structured carbons, a proprietary ionic electrolyte and improved fabrication techniques for enhanced energy density. C-Ion cells work in a manner similar to supercapacitors, i.e. maintaining their ability to provide rapid charging and long cycle life. However, C-Ion employs different carbon and electrolyte materials than current supercapacitors, which enables them to operate at higher voltages, thereby delivering energy densities that are more in line with current Li-ion batteries but without any of the fire risk or safety concerns.
ZapGo believes that it has developed the next-generation battery with four technological advantages: (1) sub five-minute charging with slow discharge; (2) increased safety; (3) significantly greater charge/discharge cycles; and (4) they are easier to recycle.
Currently-available supercapacitors have low energy densities so it has not been possible to use them to store energy over a long period of time – how has this been addressed with the new C-Ion cells?
By using synthetic carbons and nano-carbons it is possible to fabricate electrodes with controlled porosity. The amount of electrical energy that can be stored in a C-Ion cell is dependent on the surface area and electrical conductivity of the electrode, as well as the operating voltage of the electrolyte. In recent years, advances in nano-structured carbons as electrodes and non-flammable ionic liquids as electrolytes have significantly enhanced the performance.
Carbon materials have a high surface area and can be used as electrodes in electrochemical capacitors. The physical and chemical properties of synthetic and nano-structured carbon materials such as graphene, carbon nanotubes and carbon onions are of interest as these materials have large surface area, unique nano-structures and the pore size in some of these materials is below one nanometer. Nanoporous carbon has been reported with specific capacitance value as high as 284F/g (Farads per gram) and 131Wh/kg. Graphene based nanocomposites have been explored as an electrode material, and they have shown significantly increased capacitances – functionalized graphene sheets have achieved the specific capacitance value of 230F/g.
Ionic liquids are a new class of electrolyte that are stable at higher operating voltages beyond 3.0V. Ionic liquids, having a wider electrochemical window, sufficient conductivity and lower viscosity, can be used as electrolytes in C-Ion cells. Selected ionic liquid electrolytes show electrochemical stabilities up to 6V, and it is possible to tune the stability window by changing the cation-anion combinations.
Why are C-Ion cells less likely to overheat?
There are no electrochemical reactions inside a C-Ion cell that cause heat. Instead it is an ionic reaction, similar to static electricity or on the surfaces of a supercapacitor. This is also the secret of a very long life, as there is no chemistry to be used up.
How do they recharge so quickly?
Because it is an ionic reaction, there is nothing to slow it down. We recently demonstrated a cordless power tool that could be charged in 15 seconds. To do this we had to boost up the plug in the wall, because the maximum that the wall plug can deliver is about 3kW. To charge at these rates requires a higher rate of charge, so we ‘buffer’ the grid by storing energy in our cells and then when the drill needs charging, energy is transferred at very high rates.
I understand you have been testing prototypes of your C-Ion batteries in some interesting applications – can you tell us about those?
We are targeting a range of verticals, from toys and transportation to power tools and cleaning devices. We have already incorporated our C-Ion batteries into a variety of prototype products that will eventually be targeted for the consumer market. These include a functioning electric scooter; a powered bicycle energy pack; a Bluetooth five-minute charging speaker; an 18-volt power drill; and a cordless cleaner. In each of these cases, the recharge time was reduced from hours to less than five minutes. Additionally, we are aiming to incorporate our C-Ion batteries into driverless “PODs” that transport travellers at London’s Heathrow Airport, supplementing their existing lead-acid batteries, which would assist in reducing their recharge time from four hours down to 35 seconds.
When will the technology be commercially available?
ZapGo is currently focused on three key factors as it analyses potential market opportunities: revenue potential, competitive landscape, and time to market.
While ZapGo believes that there are many potential applications for its technology, current targeted products have been chosen for optimal commercial deployment in the near term. Specifically, ZapGo’s business model for the commercialization of its C-Ion technology is to partner with prominent brands in the following industries: cordless power tools and floor care products, light personal electric vehicles, and vehicle emergency start packs. Chosen partners in these sectors will incorporate ZapGo’s technology directly into their products and commercialize and sell the products under their own brand names but with ZapGo’s technology as a key differentiator, akin to the Intel Inside initiative. ZapGo believes that this strategy not only shortens time to market for this new technology but also allows it to utilize the resources of its partners to accelerate market penetration.
Following the debut of its technology at the Consumer Electronics Show (CES) in January 2017, ZapGo expects the first ZapGo-enabled products to be available for consumer purchase by Q3 2018.
What impact do you think this will have on our future?
The UK Government recently announced a total ban on the sale of new gasoline and diesel vehicles from 2040. Similar announcements have also been made in China, France, Holland, Norway and Sweden, but in some countries, the ban occurs as early as 2025. As part of this mandate, the UK Government, along with other countries, is also likely to announce incentives to encourage the uptake of EVs in the near term, mainly to improve air quality in inner cities.
Most analysts predict that there will be an inflexion point in 2025, when a new generation of battery electric vehicles will become available, that will offer similar cost and driving experience as existing gasoline and diesel vehicles. These vehicles will use new battery technology that can be charged much more quickly and provide additional driving range.
In order to gain widespread acceptance of battery electric vehicles, the automotive industry believes that drivers will demand a five-minute charge for 100-mile range and a 15-minute charge for a 300-mile range. This is possible only with ultra-fast charging 350kW (kilowatt) chargers and would mean that 30kWh (kilowatt-hours) is transferred to the vehicle in five minutes and 90kWh in 15 minutes. (Currently, it takes 10 hours to provide a 100-mile charge at home; the fastest chargers available today are the Tesla Super Chargers that can do it in about 20 minutes.)
To minimize capital investment, and to keep the price of electricity low for drivers of electric vehicles, ZapGo proposes to install large containers on filling station sites that initially contain 1MWh (megawatt-hour)1 of stored energy in its C-Ion cells. On sites with high vehicle throughput, there may be multiple containers installed. The containers will be charged up at night at off-peak rates using existing electrical connections to the site. Ultra-fast-charging 350kW chargers will be installed on site connected to the container storage, not directly to the site grid connection. Vehicles will be charged from the stored energy at the 350kW rate.
This ultra-high transfer rate is possible for two reasons:
• C-Ion can charge and discharge very quickly
• C-Ion does not catch fire, so it is safe to have a large energy store next to existing tanks of gasoline and diesel.
In summary, the new technology would provide competitively priced electricity compared to sites that have had to invest in new, expensive electrical infrastructure, and state-of-the-art ultra-fast charging capability at automotive industry rates of 350kW.