Mascot Power Blog

Lithium-titanate batteries – charging the market

The lithium-titanate battery brings some interesting fast-charging properties to the market, as Mascot launches new charging solutions for this technology.

The Lithium-ion battery has been around for quite some time now and established itself as a high performance and reliable alternative in applications from mobile phones and wearables, to electric vehicles.

In continuously pursuit of improved performance, including higher densities, charging rate, durability and ruggedness, different chemicals have been developed to meet specific requirements over a wide range of  applications.

One technology to watch out for is the lithium-titanate (LTO) battery. Lithium titanate / lithium titanium oxide (Li4Ti5O12, also referred to as LTO) is an electrode material known to have exceptional electrochemical stability. It is often used as the anode in lithium-ion batteries for applications that require high rate, long cycle life and high efficiency. LTO-based batteries are considered safer and have a wider operating temperature range.

The LTO battery is basically a modified lithium-ion battery that uses lithium-titanate nanocrystals on the surface of its anode instead of carbon. The nanocrystal structure gives the anode a surface area of about 100 square meters per gram, compared with 3 square meters per gram for carbon! This means that the electrons is enabled to enter and leave the anode rapidly, thus making a fast recharging rate possibly, providing high currents when needed.

One example to illustrate this, is the large capacity electric bus project TOSA, facilitating the fast-charging properties of lithium-titanate to partly recharge the bus battery during the short standstill at bus stops.

When considering high-capacity batteries for fast charging applications, the lithium–titanate battery brings the advantage of being faster to charge than other lithium-ion batteries. In addition, low internal resistance/high charge and discharge-rate, very high cycle life, and excellent endurance/safety. Conventional Li-ion batteries can be recharged approximately 1,000 times. The total number of recharges for a lithium-titanate battery range between 15,000 to 25,000 times (Altairnano).

The two leading companies in lithium titanate battery technology are Altairnano and Toshiba. It was Altairnano that announced the breakthrough of nano-structured lithium titanate battery technology in February 2005. They used this material to replace the carbon in conventional lithium-ion batteries and achieved better performance and a high potential for various energy storage applications.

Altairnano developed a series of lithium-titanate batteries for electric vehicle use and many electric-vehicle manufacturers announced their intention to use this new battery technology; the list includes Lightning Car Company, Phoenix Motorcars, Protera, etc. They are also currently collaborating with the US Navy in order to incorporate the new battery technology in Navy equipment. Finally, they have deployed these new energy storage systems for electric grid ancillary services as well.

Toshiba has released a lithium–titanate battery, dubbed Super Charge Ion Battery (SCiB). The battery is designed to offer 90% charge capacity in just 10 minutes!  SCiB batteries are used in the Schwinn Tailwind electric bike. Toshiba has also demonstrated its use as a prototype laptop battery. SCiB batteries are also used in a Japan-only version of Mitsubishi's i-MiEV and Minicab MiEV electric vehicles, and Honda uses them in its EV-neo electric bike and the Fit EV.
They are also used in energy storage and wristwatches (Seiko). More recently, it is beginning to find use in mobile medical devices due to its high safety.

One drawback considering LTO might be the lower energy density – compared to the Lithium-Cobalt Oxide battery often used in laptops and mobiles, with an energy density at 150 - 200 Wh/kg, the LTO battery shows energy densities at only 30 - 110 Wh/kg. This is due to a lower inherent voltage (2.4 V) than conventional lithium-ion battery technologies (which have an inherent voltage of 3.7 V

This looks even more modest when looking at the Lithium Nickel Cobalt Aluminum Oxide batteries known to be used in Tesla electric cars, which shows typically energy densities at 200 - 260 Wh/kg. But the LTO has some other advantages to balance the scoreboard.

First of all, the fast recharging rates, which might be convenient in many applications. Shortening the recharging time, whether it’s for a car or a power tool would certainly be a welcome experience for both consumers and professionals. 
The ultra-fast charging time of the LTO battery could outweigh the rather low energy density, but there are still some considerations to bear in mind. 

Even if an ordinary Li-ion battery is designed for fast charging, stressing the battery to it’s limits could degrade the battery’s capacity and ability to fast-charge over time. 
Basically, most Li-ion batteries should have no problems with fast charging from empty an up to about 50% state-of-charge (SoC). It is known that stresses occur in the second half of the charge cycle towards top charge, when acceptance of lithium ions in the anode becomes strained. 

This is why step-charging is introduced when reaching a certain level of SoC, for instance 70%, lowering the charge current gradually. It is recommended that a fast charger should be able to measure and evaluate the condition of the battery and its ability to receive charge, and adjust the charging profile continuously. Safety functions like temperature compensation and shut down should also be considered.

Based on these facts, Lithium-titanate may be a welcome alternative, as they basically allow ultra-fast charging all the way up without undue stress. This feature, which enables faster and safer recharging, is likely to be used in future electric vehicles. Charging technique is using standard constant current, followed by constant voltage until the amps threshold is reached.

The efficiency of the Lithium Titanate technology in energy storage solutions allows for a recharge efficiency of up to 98%, much higher than conventional energy storage mechanisms.  These batteries also offer the advantage in that they are able to store and deliver current peaks that are between 30 and 100 times that of ordinary lithium batteries.

The higher level of safety with LTO batteries is partly due to the lower operating voltage. But also, as the batteries are entirely free of carbon, they avoid thermal runaway or overheating which is a main cause of fires in traditional energy storage systems.

An other significant property which could be of special interest when operating in winter and/or in cold areas of the world, is the ability to work at very low temperatures, down to -40 degrees C. The low-temperature performance is due to the nanotechnology employed, and it has been shown that these batteries are able to obtain up to 80% of its full capacity at -30°C.

Analysts speculate that LTO-based batteries will dominate the market of electric vehicles in the near future. Companies such as Toshiba have started investing enormous amounts of money on this new technology. Vehicle manufacturers are seeking to invest in lithium titanate batteries in order to improve their vehicles performance. It is very likely that lithium titanate batteries will revolutionize the market the way Li-ion batteries did.



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