At present, powering cars with lithium-ion batteries, although promising, suffer from numerous disadvantages (life cycles, risks, weight, energy density, deep discharge problems, and most importantly, cost). However, innovators keep working at these problems..
Toshiba Corp developed a cell of a Li-ion secondary battery for electric vehicles. Using lithium titanate as a material for its negative electrode, the cell has an energy density as high as 100Wh/kg (See related article below).
Sample shipments will start in the fall of 2009, the company said.
Its current capacity is 20Ah and output density is about 1,000W/kg. Toshiba is currently manufacturing a 4.2Ah cell with an energy density of about 67Wh/kg for electric bicycles and other applications. The company improved the energy density by about 1.5 times by replacing lithium cobaltate previously used for the positive electrode, it said.
Toshiba has already developed a 3Ah high power cell with an output density of 4,000W/kg for hybrid cars and is now shipping its samples.
Dec 12, 2007 16:28 Kouji Kariatsumari, Nikkei Electronics
Toshiba Corp developed a Li-ion secondary battery “SCiB (Super Charge ion Battery).” The life cycle of the new battery is more than 10 years even if it is rapidly charged and discharged many times. And its safety is high.
Toshiba will begin commercial production of “TBP” series, standard modules that have 10 cells connected in series, in March 2008. The company plans to use the battery for industrial purposes such as emergency power sources, equalization power sources for wind power generators, unmanned transport vehicles and forklifts, in addition to motorized bicycles, electric motorcycles and hybrid cars.
The key feature of the Li-ion secondary battery is that lithium titanate (Li4Ti5O12) is used as a negative-electrode material with electrolyte with a high flash point and a separator with a high heat resistance. Because of this feature, a thermal runaway is less likely to occur in case of an internal short-circuit, so the risks of burst and combustion are reduced, Toshiba said.
For a positive-electrode material, lithium cobalt oxide (LiCoO2) was adopted as in the case of Li-ion secondary batteries for portable devices.
In the presentation, the movie of an external short-circuit test was shown. Even in the case of the external short circuit, the temperature of the cell did not go over 100°C, explode or catch fire.