2781cal response. This is certainly the case for the above system since the Li~NiOx/WQ eleetroehromic cell can be cycled several thousand times with about 50% change in optical transmission. 23 Some concern could still be addressed to the charge-discharge rates since they directly influence the device's response time. However, for most applications, response times of the order of one or few seconds are appropriate and thus even materials with relatively slow lithium diffusion rates are still acceptable, providing they offer the required optical properties.Therefore, the first generation rocking chair batteries, proposed in the early eighties as novel lithium, low-rate reehargeable systems capable of offering long cycle life, 3 have indeed found continued interest. So, the old concept does hold. The question is whether the new concepts for rocking chair batteries, proposed as alternatives to highenergy, high-power lithium and nickel-cadmium batteries, 13't4 will eventually find their way in the competitive portable power source market.