Many makers are penetrating into the EV market. The common problem is the paucity of capacity of lithium-ion battery. The running distance of “i-MiEV”, which is made by Mitsubishi Motors and mounts the battery, is only 160km on one full charge. It is inadequate for the long running distance.

 Indeed the performance of lithium-ion battery has advanced drastically after its development by SONY in 1991, but it is almost impossible to develop the EV which can run the same running distance as gasoline car. Therefore, the generational shift related to materials, which constitute the battery, has started.

 Usuallithium-ion battery consists of four parts, i.e. positive-electrode material, negative-electrode material, electrolytic solution and separator. By the movement of lithium-ion from negative-electrode material to positive-electrode material at the time of discharge, an electric energy occurs. The reverse phenomenon occurs in case of charge. In such situations, an electrolytic solution transmits the movement of ion. And then a separator prevents its short circuit by separating between positive-electrode material and negative-electrode material. A maker has to combine these four parts suitably in order to increase its performance.

 A cobalt system compound has been used for its electrode material for a long time. Recently, the price of cobalt has risen sharply, so many makers make efforts to find alternative material. Panasonic paved the way for the increase of its capacity by using nickel system compound. In 2006, Panasonic started to mass-produce of “18650 battery”, which is cylindrical one with the size of 18mm in diameter and 65mm in length and is used for note-PC and so on. Comparing with usual one, its capacity is improved by 10%. “Tesla Motors, Inc.” in USA had already developed and released EV with thousands of 18650 batteries. And also SONY developed the positive electrode by using olivine iron phosphate (LixFePO4). It has reasonable cost and splendid performance.

 Makers had better consider not only the improvement of positive electrode but also that of negative one in order to improve the performance of battery. Indeed Carbon has been used for the material of negative electrode for a long time, but they see the end coming. They expect Silicon as alternative material. Although it has ten times of performance of Carbon, it has the defect that it is swollen if it absorbs lithium ion. If it is repeated charge and discharge, its plate is destroyed and then its performance becomes depleted. Panasonic will overcome this defect soon. It could be solved the problem related to the deformity of plate by using alloyed material, which consists of Silicon, Tin and so on. Mitsui Metal is making similar efforts.

 They have to improve electrolytic solution, too. The electrolytic solution used for lithium-ion battery is combustible organic solvent. If they increase the capacity, the ignition risk increase, too. “Daikin Industries, Ltd.” developed the new addition agent by making use of fluorine compound, which is used for the primary fluid of air conditioner. If they add this one into electrolytic solution, they can prevent its ignition risk and explosion. “Showa Denko K.K.” co-developed the safety electrolytic solution with US company and will deliver its sample within this year.

 The improvement of present lithium-ion battery has some limitation. Therefore, some makers are developing the new-generation battery. It is the lithium-air battery, which has the negative electrode made of metallic lithium and generates electric power by reacting it with oxygen at positive electrode. There is no need to sardine positive-electrode material within battery. Because oxygen can be obtained from an air unlimitedly. And then its energetic density can be elevated drastically. EV can run with the same running distance as that of gasoline car if it uses this battery.