Rechargeable batteries

As a matter of fact, most of our technical electrochemical energy storage s ystems opera re outside the limitations of thermodynamics. As in the case o f rechargeable batteries with aqueous electrolytes (part I of this article) , kinetics control the operation and safety also in batteries with nonaqueo us electrolytes (this second and final part). A striking example is the lit hium ion battery which possesses an operating voltage of >3,5 V and a very high energy density. From a thermodynamic viewpoint such a cell is impossib le because the used organic electrolyte is in contact with two lithium inse rtion electrodes that operate at extreme reducing and oxidizing potentials, respectively. However, a unique mechanism kinetically prevents the decompo sition of the electrolyte due to the formation of electronically insulating interphases between electrode and electrolyte that are still permeable to the electrochemically active Li+ cations. Lithium ion batteries have alread y made their break-through into the market as small format sq stems for por table electronics. The only "kinetically shielded" high energy density howe ver, might be a safety complication for large format batteries, which are a ssembled for electric vehicle (EV) propulsion. Safety concerns are also val id for high temperature (300 degrees C) batteries such as the sodium-sulfur and sodium-nickel chloride systems. These systems are still in the stage o f "experimental batteries", which may find future application in large unit s fur EV's or uninterruptible power systems. The paper is concluded by a pe rformance comparison of various rechargeable battery systems with aqueous a nd nonaqueous electrolytes. (Possible) applications in consumer electronics and EV's are discussed in more detail.