Dr.-Ing. Arnold Lamm, Senior Manager Characterisation HV-Storage Systems at Daimler, presented a modular approach analysis of the design of Li-ion batteries for PHEV applications based on cell design and chemistry, cooling systems, life and performance aspects and cost. He concluded that, for PHEV batteries, the usable energy per litre of PHEV battery should be greater than 70 Wh/L, the volumetric energy being more important than the gravimetric energy. The choice of chemistry depends on the vehicle requirements, whether 30-35km or 50km.
In terms of safety, especially when considering the regulation requirements of the Chinese market, Li-ion batteries based on FePh04-chemistry exhibit the best results. Batteries with this chemistry also have higher cycle life than NCM based batteries, which require additional safety elements (ceramic separator, shuttles, CID, etc.) in the cell when used for a vehicle range of 50km. The energy throughput of PHEV batteries ranges between 65 MWh and 100 MWh, which is twice as high as for EV batteries. Concerning cooling, contact between the water/glycol and HV-path must be prevented. Due to the volumetric energy density, air-cooling is not an option.
Lamm concluded his presentation with a look at cost aspects. He believes that €300/kWh is possible by 2020 (compared to EV batteries which, at high volumes, can reach €220/kWh).
Li-ion technology evolution for Evs: How far and how fast?
Menahem Anderman, President of Advanced Automotive Batteries (AAB) presented on the current status and future prospects of High-Voltage HEVs, Low-Voltage Systems and PHEVs & EVs, highlighting both pros and cons of each. Anderman found that Li-ion is the preferred energy storage solution for most EV architectures. With high reliability, long life and no safety issues, high-voltage HEVs – NiMH – are not expected to face much competition in the next 10-12 years.
The major design drivers differ for each application. The main opportunities for high Voltage HEVs lie in improving low-temperature power, reducing power fade, improving power and DOD range and simplifying electronics and cooling. In low-voltage systems, low-temperature power and charge acceptance, as well as pack related complexity and cost, are the areas that require improvement. PHEVs need to increase usable energy over a 10-year lifetime and EVs require improvement in energy density and calendar life at full SOC. For all applications, the common design matrix includes reducing material, cell and pack cost.
Status of LIB industry in China and its readiness to support the EV market
Xiaoyu Zhang, RealLi Research Europe, presented an overview of the Lithium-ion (LIB) battery market in China, which has a 26.5% market share and 9.2% exportation rate for total battery production. At the moment, China urgently needs raw materials for power LIB. While LFP remains the competent material for ESS, it will face challenges from LMO and LTO in the future. Chinese requirements concerning battery energy density have encouraged a trend toward replacing LFP with LMO/NMC for EVs.
Zhang believes that module technology for LIB packing needs to be greatly improved in the future and appropriate business models should be implemented in different cities. LIB/OEM players have to be aware of the government’s intentions, not only focusing on funding applications. Futhermore, increased attention must be paid to LEV and customer interests.
Photo courtesy of Tal Lee Anderman - AABC Europe 2013