The major bottleneck for battery driven electric vehicles is the battery. Existing battery types all have their specific drawbacks: lead acid batteries give a short range, NaS batteries operate at 300 C and NiCd batteries contain poisonous Cd and are expensive. Li batteries may achieve a range of 200-300 km, operate at room temperature and are expected to be cheap. The EC programme therefore focuses on the development of different concepts for Li batteries. This project will develop a lithium battery with a lithium-carbon intercalation anode, (the SWING or Lithium Ion system) and a solid polymer electrolyte. The feasibility of such a system for electric vehicle traction applications will be demonstrated. The performance targets are for energy density: 150 Wh/kg (lead acid batteries have 30 Wh/kg) for power density: 150 W/kg and for the lifetime: 300 deep discharge/charge cycles.
Replacing the metal anode with a Li-carbon intercalation anode (the SWING system) produced a reversible capacity of only 100 mAh/g at high operation temperatures. This specific energy is lower than the liquid electrolyte system where 300 mAh/g was achieved at the negative electrode. The increasing impedance of high temperature cells led to relatively low rate capability of these cells compared with the liquid electrolyte system. During the experiments, a good cycle performance (1000 cycles) from Li-ion polymer batteries using plasticised polymer electrolytes was achieved. However, this cycle life reduced to only 200 cycles if the criterion for end-of-life was set at 80% of initial capacity, which is the usual value.
The development of rechargeable lithium batteries has been hampered by a very limited cycle life and safety problems associated with the formation of lithium dendrites at the lithium metal anode. Replacing the metal anode with a lithium-carbon intercalation anode (the SWING or Lithium Ion System) solves these problems.
Small cells with a liquid organic electrolyte developed by VARTA Batterie AG have demonstrated a cycle life exceeding 1000 deep cycles and acceptable safety behaviour.
The advantage of solid polymer electrolyte (SPE) cells are the potential for low cost manufacturing and the simple cell construction possible due
In this project, VARTA's expertise on SWING electrodes and AEA's expertise on solid polymer electrolytes will be combined. The tasks include SWING electrode material development (VARTA), composite electrode development (AEA and VARTA), laboratory scale cell development and testing (VARTA and AEA). The University of Rome will have the responsibility for the evaluation of non-carbon materials for the use as anodes in the SWING system.
The performance targets are an energy density of 150 Whkg-1 and a power density of 150 Wkg-1. The laboratory scale cells will have a capacity of approximately 200 mAh. It is excepted that a minimum of 300 deep discharge / charge cycles with a maximum charge time of l0 hours will be demonstrated.
The results of this project will flow into a second project which will scale up laboratory scale process to pilot scale and battery size to 2 kWh to demonstrate feasability of Lithium Polymer and SWING Polymer batteries for Electric Vehicle Traction.
Funding SchemeCSC - Cost-sharing contracts
OX11 0RA Didcot - Oxfordshire