When this blog last looked at a battery and super-capacitor combination, it was with a product that extended the life of lead acid batteries. Green Car Congress relays word that Mitsubishi Electric Corp has demonstrated prototypes of a hybrid energy storage cell that combines EDLC (electric double layer capacitor) capability with Li-ion battery in a single cell.
The devices feature an anode shared by the capacitor and the battery, each of which have a cathode and a separator… The key to realize the new device is the structure of the shared anode… The anode is made with carbon material. The capacitor cathode was made with activated carbon, and the battery cathode was made with a lithium-iron phosphate material.
GCC commentator Engineer-Poet cautions that “the test units only hit 2000 cycles before reaching 20% degradation, but the article doesn’t state the depth of discharge. Shallower cycling would almost certainly increase the lifespan a great deal.”
Limiting the units to their 8C rate, at 2.4 kW/kg a 30 kg pack would supply 72 kW; nearly 100 horsepower. This is enough to accelerate a substantial vehicle at a good pace, and can brake a 1500 kg vehicle from 45 MPH to 0 in 4.5 seconds (if traction is no limit). A Prius-class vehicle could use a smaller engine and bigger motors to achieve both higher performance and superior economy with a similar battery weight.
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