Chaired by Ted J. Miller, Senior Manager of Energy Storage Strategy and Research, Ford, Session 3 of AABTAM focused on battery design and performance data from EVs and PHEVs. cars21.com provides a summary of the presentations in this second update from the Advanced Automotive Battery Conference (AABC), organised in Pasadena, California, 4-8 February 2013.
Honda Fit EV battery pack
Akihiro Anekawa, Chief Engineer, Honda R&D, presented the battery system for the latest BEV of Honda, the FIT EV. In this car, the 20 kWh Li-ion battery made by Toshiba is located under the passenger seats. A Toshiba battery is used because it is a high-density battery, using lithium titanate for negative electrode, ensuring greater durability.
Each battery module is designed to efficiently air-cool the battery undersurface. The battery box case itself is also designed to allow cool air to flow inside the battery box and in between battery modules. Heat transfer materials are used to efficiently transfer the heat from the battery to the battery box.
According to Honda R&D, such a cooling system improves daily and long-term usage:
- Daily usage: the cooling system allows more stress to be put on the battery (when repeating cycles of driving on highways and charging, for example) without risking overheating the battery system.
- Long-term usage: a better cooling system improves the durability of the battery.
Advances in Toshiba LTO-based battery SCiB
SCiB technology is characterised by a LTO (lithium titanate) anode whose crystal structure is stable in volume change dependent on SOC. It can be operated safely and has a long life even at low temperatures since there is little risk of lithium metal plating.
This technology powers some Mitsubishi EVs (some iMiEVs and Minicab EVs) and was recently selected to power Honda’s FIT EV.
Toshiba expects to improve the current energy density of SCiB cells by 150% thanks to to the development of Ti-based new anode material.
"Regarding durability, it has been already been proven that the SCiB technology can run for over 20,000 cycles in practical conditions of 10C/10C 20-80% charge-discharge at 35°C."
AESC Battery Production and Technology Status Update
AESC produces both High power and High energy cells, for HEV and EV applications, respectively. Their high power battery for the HEV Nissan FUGA Hybrid is composed of 12 modules in series of 8 high power cells in series. Their high energy batteries are composed of 48 modules in series of 4 cells in 2 parallel-2 series.
AESC battery design maximises battery performance and thermal management by maintaining a very high level of safety, thanks to the “Safety shield” concept. The vehicle and the pack are designed as multiple protective shields against hazardous impacts. Cell and module are designed to obtain sufficient resistances as a margin.
In the recently released new version of the Leaf, the battery pack has greatly changed. AESC reduced the weight from the whole pack by 30kg. Each module is 70g lighter. Great weight reduction came also from Junction Box (from 2,6kg to 1,5kg) and Service Disconnect SW (from 650g to 412g).
Lisnen battery technology Roadmap
Lisnen is a company with 14 years’ experience in the Li-ion industry, and has already shipped 1 billion cells worldwide. At AABC 2013 they shared with the audience their Battery technology Roadmap, for the cell, BMS and system level.
Today Lisnen’s cells have a density of 130Wh/kg, using LFP anodes and C cathodes, and conventional electrolyte LiPF6. In 2015, Lisnen wants to reach a density of 200Wh/kg and 300-400Wh/kg in 2020. By 2015, the company wants to use:
- Anode: high voltage LiNiMn04/LiNiMn02 or 5V Li-rich layered material, LiNiPO4, etc.
- Cathode: C+HC/SC Ceramic coating, C+Si alloy/Sn+Si alloy or Li.
- Electrolyte: 5V Electrolyte/Gel or Ionic Liquid.
Regarding their BMS technology, many developments are planned by 2015, including ultra-capacitor CMS (based on BMs technology), light industrial ESS BMS, and active balancing, and for the whole system level, improving the liquid thermal management for both cooling and heating applications.