Samsung Yokohama Research Institute Co Ltd delivered a lecture on its efforts to improve the performance of lithium-ion rechargeable batteries using a solid solution-based positive electrode material.
The lecture was delivered at LLIBTA, a conference that took place along with AABC 2012, which ran from Feb 6 to 10, 2012, in Orlando, the US. The company calls Li2MnO3-LiMO2 (M: metal such as Ni, Mn and Co), which is a solid solution-based positive electrode material, OLO.
There were two problems with the OLO. First, cells made by using an OLO inflate because of the gas generated when they are charged for the first time. Second, because they are charged with a high voltage, their capacities drastically deteriorate after their charge/discharge cycles are used up.
Samsung Yokohama reduced the amount of the gas by 98% by improving the method of synthesizing the positive electrode material. It also drastically reduced the amount of oxygen generated inside the cell by making improvements to the graphite used as a negative electrode material.
Furthermore, to improve charge/discharge cycle, Samsung Yokohama made improvements to a separator and battery electrolyte. Specifically, while oxidative destruction took place at a voltage of 4.35V or higher with the separator in the past, the company reduced the reaction by forming a protective layer on the surface of the separator. And, for electrolytes, the company employed fluorinated carbonate- and ether-based materials so that they do not dissolve at a high voltage.
Samsung Yokohama ensured a comparative capacity of 250mAh/g or higher (for the first discharge) with a laminated cell prototyped by combining an improved OLO, graphite, separator and electrolyte. As for its charge/discharge cycle properties, the company maintained 87% capacity after 400 cycles at a normal temperature (25°C).
In a more demanding charge/discharge cycle test that Samsung Yokohama had by using a coin-type cell under a temperature of 45°C, its capacity was 87% after 200 cycles. So, it is a lithium-ion rechargeable battery that can be used for practical applications, the company said.
Written by Kouji Kariatsumari