Toshiba Discusses Li-ion Battery Using LTO-based Negative Electrode

Feb 19, 2013
Kouji Kariatsumari, Nikkei Electronics

Toshiba Corp delivered a lecture on its lithium-ion (Li-ion) rechargeable battery using lithium titanate (LTO) as a negative electrode material under the title of "Advances in Toshiba LTO-based battery 'SCiB' and its applications" at AABC 2013, which took place from Feb 4 to 8, 2013, in Pasadena, the US.

Referring to the SCiB, Toshiba said that Li ions are desorbed and inserted in the crystalline structure of LTO and that its electrodes swell less than the negative electrodes of carbon materials due to charging, contributing to longer life. Furthermore, because of the high electric potential for Li, Li does not precipitate at negative electrodes even when the battery is charged at low temperatures, realizing a high safety and excellent low-temperature properties.

Currently, Toshiba has a 20Ah product for electric vehicles (EVs) and plug-in hybrid vehicles (PHEVs) and a 3Ah product for no-idling vehicles and hybrid vehicles.

20Ah product
The average voltage and energy density per volume of the 20Ah product are 2.3 V and 176Wh/L, respectively. It measures 103 x 115 x 22mm. At this point, 10.5kWh of cells are mounted on Mitsubishi Motors Corp's "i-MiEV M" and "Minicab-MiEV CD," and 20kWh of cells are used for Honda Motor Co Ltd's "Fit EV." Also, Toshiba is now developing a cell for electric buses.

Toshiba plans to start to supply a next-generation cell made by combining a titanium (Ti)-based high-capacity negative electrode material and a positive electrode material that has a higher capacity than the current ternary material in 2014. With the next-generation cell, the company will achieve an energy density of 250Wh/L or higher while keeping the voltage.

When the dimensions of the cell are the same, it is possible to realize a 30Ah product, the company said. It expects to develop a 35Ah product with an energy density of 300Wh/L or higher in the future.

3Ah product
The 3Ah product, which is targeted at high-output applications, has an average voltage of 2.4V. With an SOC (state of charge) of 50%, its 10-second output and input are 450W and 476W, respectively.

The dimensions of the 3Ah product are 96 x 62 x 13mm. At a temperature of 35°C and with an SOC of 20-80%, it maintains 80% or more of the initial discharge power after 20,000 or more charge/discharge cycles (10C).

The cell was employed for the idling stop mechanism of Suzuki Motor Corp's Wagon R. Denso Corp developed a battery module consisting of five cells connected in series and is supplying it to Suzuki. Denso plans to sell the module for hybrid vehicles including 12-48V micro-hybrid vehicles.