Introduction to Hitachi’s Lithium Battery Energy Density Doubling Technology

　　According to Nikkei Manufacturing, Hitachi has recently developed a technology that can more than double the energy density of lithium ion secondary batteries (LIB). By making the thickness of the positive electrode twice the original, the 30Ah battery cell has achieved an energy density of 335Wh/kg. This technology is expected to double the distance that a pure electric vehicle (EV) can travel on a single charge.

　　According to Nikkei Manufacturing, Hitachi has recently developed a technology that can more than double the energy density of lithium ion secondary batteries (LIB). By making the thickness of the positive electrode twice the original, the 30Ah battery cell has achieved an energy density of 335Wh/kg. This technology is expected to double the distance that a pure electric vehicle (EV) can travel on a single charge.　　 reported that the development this time is LIB that uses nickel-based materials for the positive electrode and silicon (Si) -based materials for the negative electrode. The positive electrode is pressed into a film to increase the amount of lithium ions, thereby achieving high energy density. However, only the lamination process will cause uneven distribution of active materials, resulting in insufficient movement of lithium ions. Therefore, Hitachi uses a scanning electron microscope to observe electrode slices and visualize the three-dimensional structure of the electrod e based on the observed information, thereby developing a film forming technology that can uniformly distribute active materials, binders, and voids. In addition, in order to suppress the decomposition of the electrolyte solution during the high-voltage treatment, the particles of the positive electrode material are also coated with an oxide film to prolong its life.　　In order to use silicon-based materials for the negative electrode, Hitachi newly developed a high-strength binder this time, which can achieve a strong bond between particles of silicon-based materials that form a conductive film. As a result, as the negative electrode material of LIB, silicon material is expected to achieve the same life span as ordinary carbon materials. Although silicon-based materials have a large amount of lithium ion adsorption, they also bring about the problems of large volume expansion and easy separation of the material from the negative electrode.　　 This time, Hitachi used the above methods to make the energy density of the battery cell reach 335Wh/kg, which is 2.6 times that of the company's previous products, and the output power density has also reached 1600W/Kg. Calculated based on the weight of the battery unit being 150kg and the power consumption being 114Wh/km, compared with previous products, this new type of battery can double the EV's cruising range.　　 The current problem with this battery is the charge-discharge cycle life. The current life is up to 50 cycles, which is the same as LIB using carbon material as a negative electrode, but to be equipped with an EV, the life must reach 3000 cycles. In the future, Hitachi will continue to promote technology development to extend life, improve stability and safety, and the goal is to put the technology into practical use in 2020.