Introduction to Energy Density Double Technology of Hitachi Lithium Battery

According to the Nikkei Manufacturing Report, Hitachi Manufacturing Co., Ltd. recently developed a technology that can more than double the energy density of lithium ion secondary batteries(LIB). By twice the thickness of the positive electrode, the 30Ah class battery unit achieved a energy density of 335 Wh/kg. The technology is expected to double the range at which pure electric vehicles(EVs) can be recharged once.

The report said that the development of positive poles using nickel materials and negative poles using Silicon(Si) materials LIB. The lithium-ion content is increased by pressing the positive electrode to achieve high energy density. However, only pressing film treatment can lead to uneven distribution of active substances, resulting in insufficient movement of lithium ions. Therefore, Hitachi made use of a scanning electron microscope to observe the electrode section and visualized the three-dimensional structure of the electrode based on the observed information, thus developing a membrane molding technology that can evenly distribute active substances, adhesives, and voids. In addition, in order to suppress the decomposition caused by the electrolyte during high-voltage treatment, the oxide film is also used to coat the particles of the positive electrode material to extend its life.

In order to use Silicon materials in the negative electrode, Hitachi has developed a new high-strength adhesive to achieve a strong combination of particles that form conductive films of Silicon materials. In this way, as a negative electrode material of LIB, Silicon materials are expected to achieve the same life span as ordinary carbon materials. Although Silicon materials have a large amount of lithium ion adsorption, this also brings problems of large volume expansion and material easy to be stripped from the negative electrode.

Through the above means, Hitachi's energy density of the battery unit reached 335 Wh / kg, which is 2.6 times that of the company's previous products, and the output power density reached 1600W/Kg. Calculated by a battery unit weight of 150kg and a power consumption of 114 Wh/km, this new type of battery can double the EV range compared to previous products.

At present, the problem of this kind of battery is the cycle life of charge and discharge. The current life is up to 50 cycles, which is the same as that of the LIB with a negative electrode of carbon material. However, to be equipped with an EV, the life must reach 3,000 cycles. In the future, Hitachi will continue to promote technology development to extend life span, improve stability and safety. The goal is to put the technology into practice by 2020.

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