ABSTRACT
Electric vehicles (EVs) with rechargeable batteries are considered to reduce CO2 emissions and the consumption of fossil fuels because the total energy conversion efficiency of batteries is higher than that of internal combustion (IC) engines. The average tank to wheel energy efficiency of the U.S. fleet is 12.6%, while the efficiency of battery to wheel is approximately 90% [1]. Many types of batteries such as improved lead-acid [2], sodium-sulfur [2,3], metal-air [2], lithiumpolymer [4], nickel-metal hydride [5], and lithium-ion [6] have been developed over the last half century. The first EVs were developed at the end of the nineteenth century and employed lead-acid batteries. The lead-acid battery was developed
2.1 Introduction .................................................................................................... 21 2.2 History ............................................................................................................23 2.3 Type of Lithium-Air Batteries .......................................................................25 2.4 Nonaqueous Lithium-Air System .................................................................. 29
2.4.1 Electrochemical Reaction in the Nonaqueous Lithium-Air System ...... 29 2.4.2 Stability of Nonaqueous Electrolytes for Rechargeable
Lithium-Air Batteries ........................................................................30 2.4.3 Cell Performance of Rechargeable Nonaqueous
Lithium-Air Batteries ........................................................................ 37 2.4.4 Electrode Catalysts ............................................................................. 41 2.4.5 Further Problems for Nonaqueous Lithium-Air Batteries ................. 42
2.5 Aqueous Lithium-Air System ........................................................................ 43 2.5.1 Concept of Aqueous Lithium-Air System ......................................... 43 2.5.2 Water-Stable Lithium Ion Conducting Solid Electrolytes ..................44 2.5.3 Protective Interlayer between Water-Stable Solid Electrolyte
and Lithium Metal .............................................................................. 49 2.5.4 Cell Performance of Rechargeable Aqueous
Lithium-Air Batteries ........................................................................ 51 2.6 Summary ........................................................................................................ 58 References ................................................................................................................ 59
in 1859 by Planté. Lead-acid batteries are generally inexpensive and have a high power density; therefore, they have been used most widely for starting, ignition, and lighting of vehicles. The calculated energy density of lead-acid batteries is 171 Wh kg−1 and 370 Wh L−1 and the packed energy density of the sealed batteries for EVs is as low as 35-60 Wh kg−1 and 94-108 Wh L−1 [2]. The driving range for a compact EV with 14.4 kWh batteries is 110 km for a full charge. In 1989, Panasonic Ltd. and Sanyo Ltd. of Japan commercialized an advanced rechargeable nickelmetal hydride battery. The energy densities of the packed metal hydride battery were 48-63 Wh kg−1 and 82-142 Wh L−1. The Toyota RAV4 EV with 27 kWh nickel-metal hydride batteries could drive for 178.5 km, where the 451 kg battery was 28.5% of the total car weight. In 1990, Sony Ltd., Japan, commercialized lithium-ion batteries with an even higher energy density. These batteries consisted of a carbon anode, a nonaqueous electrolyte, and a LiCoO2 cathode. The reversible cell reaction is as follows [7]:
LiCoO2 + 2.7C = Li0.55CoO2 + 0.45LiC6 (2.1)
The cell voltage during operation is 3.9 V and the calculated specific energy density is 361 Wh kg−1. The specific calculated energy density of a gasoline engine for automotive applications is estimated to be around 1700 Wh kg−1, determined using the reaction heat of gasoline and a tank to wheel efficiency of 12.6% [1]. The calculated energy density of lithium-ion batteries is thus only one-fifth that of gasoline engines. To achieve EVs with comparable driving ranges to gasoline engine vehicles, battery systems with theoretical energy densities greater than 1700 Wh kg−1 should be developed. Lithium-ion batteries have been extensively used for the recent EVs because they have the highest energy density of batteries developed to date. However, the driving range of these EVs is still too short compared to vehicles with IC engines. The Nissan LEAF EV commercialized by Nissan Motors Ltd. was announced with driving range at full charge of 228 km without air conditioning and 130 km with it, where the total car weight was 1520 kg and the battery weight was around 240 kg. The specific energy density of the lithium-ion batteries used for the Nissan LEAF is around 100 Wh kg−1, which is approximately 30% of the calculated specific energy density for the lithium-ion battery.
