Toshiba Developing 3.0 Ah High Power SCiB Li-Ion Cell for HEV Applications
21 May 2008
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| A 140-cell pack of Toshiba’s 3.0 Ah SCiB cells meet the FreedomCAR HEV power assist goals. Click to enlarge. |
Toshiba, which last December announced the general commercial launch of a 4.2 Ah cell version of its fast-charging SCiB—Super Charge ion Battery—lithium-ion battery (earlier post), is developing a 3.0 Ah high-power version of the cell specifically for hybrid electric vehicle (HEV) applications.
Shinichiro Kosugi, Chief Specialist for Toshiba’s Super Charge Battery Division, described the characteristics of the HEV cell during a presentation at the Advanced Automotive Battery Conference (AABC) last week.
Toshiba uses a lithium titanate (LTO) material in its anode for improved safety and support for fast recharge. An LTO anode supports high rate capabilities and fast charge even at low temperatures.
| Toshiba SCiB LTO Cells | ||
|---|---|---|
| SCiB 3.0 | SCiB 4.2 | |
| Format | Prismatic | Prismatic |
| Nominal voltage | 2.4 V | 2.4 V |
| Operating voltage @ >0°C | 2.8-1.7 V (2.8-1.5 V <0°C) |
2.8-1.7 V |
| 10s discharge power @BOL, 50% SOC, 25°C | 500 W (3,600 W/kg) |
170 W (1,100 W/kg) |
| 10s charge power @BOL, 50% SOC, 25°C |
400 W (2,900 W/kg) |
230 W (1,500 W/kg) |
| Discharge capacity (1C) | 3 Ah (51 Wh/kg) |
4.2 Ah (65 Wh/kg) |
| AC impedance (1kHz) | 1.7 mΩ | 2.6 mΩ |
| 10s DC resistance @BOL, 50% SOC, 25°C |
2.5 mΩ | 6.5 mΩ |
| Weight | 140 g | 155 g |
| Size (mm) | 62 x 90 x 13 | 62 x 95 x 13 |
| Application | HEV | General |
However, cell voltage is only 2.4 V (the anode is 1.4 V versus lithium) and it has a low capacity density of about half that of graphite.
It is, however, inherently more thermally stable than conventional carbon anodes.
Toshiba designed the 3.0 Ah cell specifically for automotive applications. The can material is lightweight aluminum, with high cooling efficiency (although more difficult to weld). Toshiba uses a laser weld for tightness and reliability rather than a crimp or hermetic seal. Terminal sealing uses resin caulk.
The terminal-busbar connection is welded for low resistive loss and high reliability, and the terminals are on one side of the cell for simplified connection and aggregated leak risk.
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| The SCiB HEV battery compensates for lower voltage and capacity by having a larger SOC window. Click to enlarge. |
Although the cells have a lower voltage and capacity than other lithium-ion battery technologies, the LTO chemistry compensates for that by offering a larger functional state of charge range. (This is an argument similar to that proposed by EnerDel, which also uses an LTO anode chemistry. Earlier post.)
Although a pack comprising Toshiba 3.0 Ah SCiB cells would require 140 cells to meet the FreedomCAR power assist targets—150% more than conventional lithium-ion battery (LIB) technology—the pack would require 20% less material, according to Toshiba.
Dr. Menahem Anderman, president of Advanced Automotive Batteries, suggests that batteries with lithium titanate anode materials may be of interest in high-power, ultra-long-life, low-energy applications—e.g., micro and mild hybrids—in competition with ultracapacitors.
How much mileage does that translate into, say in a Prius?
Posted by: thomas | 21 May 2008 at 04:28 AM
I wonder if this chemistry can be used in conjunction with Maxwell's dry processing technique. Cheap high power low energy batteries would be a nice first step.
Posted by: GreenPlease | 21 May 2008 at 04:32 AM
The FreedomCAR is a hydrogen based initiative. This gives you the Freedom to buy your Hydrogen fuel from the BIG energy companies because hydrogen is way too dangerous to make and handle for a personal operation. Obviously the FreedomCAR battery specification is designed as a temporary storage medium for occasional acceleration, necessary because the hydrogen fuel cell cannot supply power on demand.
However, any improvement in large battery capacity and reduction in price and weight is good news. We might eventually see some of the new technology being used in a BEV.
So ... Toshiba ... how much will your new 3.0 Ah SciB cells cost and weigh per kWh of electrical storage?
Posted by: John Taylor | 21 May 2008 at 04:48 AM
So the way I get it is that the SOC window is the percentage of usable energy in a battery that allows for maximum battery life in the sense that it minimizes the ‘cost of ownership’. More specifically, the SOC window should be the percentage of usable energy that maximizes the following ratio ((cumulated kWh obtainable from charge-discharging the battery at SOC until it reaches a certain capacity level e.g. 80% of original capacity in kWh) / original capacity in kWh). Or did I miss something?
So the reason the Volt uses a 50% SOC window (on both A123 and LM?) is that it is the percentage that maximizes battery life in the sense of maximizing the cumulative kWh that can be delivered by the battery throughout its lifetime. In principle you could operate the battery using 100% depletion for every cycle (and get 80 miles of electric only range at day one at least) but the result would be a very short lived battery perhaps only 2 years using a typical driving duty for the Volt. Not very nice if you need to pay $8000 for a new 16 kWh pack.
This SOC window is kind of important they should report it as a matter of routine. Alternatively, report usable Wh/kg as well as ordinary Wh/kg. For example
Thoshiba SCiB 4.2:
Ordinary: 65 Wh/kg
Usable: 52 Wh/kg (0.8*65)
A123:
Ordinary: 110 Wh/kg
Usable: 55 Wh/kg (0.5*110)
Posted by: Henrik | 21 May 2008 at 05:22 AM
Henrik:
Agree with you that energy density storage should be expressed in Total and Usable Wh/Kg.
Max Power vs Time + Max number of cycles (to 80% of performance) + price per KWh of Usable energy stored should also be stated.
For stop and go city type traffic it seems that supercaps could help to increase usable energy storage and extend battery life in most cases, but would cost and weight more unless batteries could be made smaller to compensate.
Eventually, improved batteries may not need supercaps to handle large regenerative breaking energy and frequent large discharges to accellerate a vehicle in down town traffic.
Posted by: Harvey D | 21 May 2008 at 07:17 AM
Very true, we need to know a couple of things.. the "usable" capacity, the weight, the cost.. how many cycles it will last at that capacity level and if there is a calendar limitation on the life of the battery. Without all this all you get is a useless public relations release. Some batteries also experience changes in internal resistance as they age.
Of course they may just not know how many cycles they would get at a particular "capacity" level.. most of the cell heating happens when they are nearly discharged.
Posted by: Herm | 21 May 2008 at 07:58 AM
Henrik, battery life is dependent on power drain. You can do high power at 50% SOC for a brief time with little effect, but even medium power at 10% SOC for a long time might severely degrade the battery. This makes a simple SOC-window times cycle-life calculation, by itself, somewhat useless.
Posted by: doggydogworld | 22 May 2008 at 11:40 AM
Does any one know how much power an EV use ? Does the acces power cabels have the capasity ? What will happen when every house on the road plugs 2 EV in to the net between 5 and 6 pm ? Do we need to build a new "last mile" power infrastructor ? and how about all the transformers ? - uffe
Posted by: Uffe Gramm Mogensen | 02 March 2010 at 03:51 PM
Does any one know how much power an EV use ? Does the acces power cabels have the capasity ? What will happen when every house on the road plugs 2 EV in to the net between 5 and 6 pm ? Do we need to build a new "last mile" power infrastructor ? and how about all the transformers ? - uffe
Posted by: Uffe Gramm Mogensen | 02 March 2010 at 03:51 PM