NGK refers to the solid-state battery as a "chip-type ceramic secondary battery." Its ability to work at high temperature enables the battery to be closely apposed with chips on a circuit board.
As a solid-state battery does not use liquid electrolyte, the risk of liquid spills does not arise. But it is considered difficult to achieve high density as the ion conductivity of the electrode is low because of the disorder of the crystal structure. Since the random crystal orientation of conventional batteries' electrodes hampers smooth lithium-ion movement, it is difficult to make the electrode thick.
NGK has been manufacturing ceramic insulators since 1919. Based on its accumulated ceramic technology, researchers at the company developed a ceramic plate whose crystal orientation is rigorously aligned and fired.
Because the crystal orientation of NGK's ceramic plate is controlled, movement of lithium ions is smooth and fast, meaning the plate's ion conductivity is high, says the manufacturer. The positive ceramic electrode can have a much thicker layer than that of conventional electrodes, about 10 times thicker, and so it can store far more lithium ions. Today's prototype measures 13x13x0.2mm and its energy density is more than 300Wh/L, around 10 times higher than that of conventional solid-state batteries, according to the company.
NGK expects the characteristics of high-temperature operability and high density will expand the application field to include new areas where conventional solid-state batteries cannot be used.
For example, a smaller version of the battery can be closely apposed with semiconductor devices such as ICs, memories or diodes on a circuit board, which helps reduce the size of electronic devices. Smart cards, wearable devices, and solar wrist watches are also potential applications. NGK intends to offer samples by the end of this fiscal year, March 2015.
Reflecting demand from customers and requirements for specific applications, the company plans to begin volume production and commercialize products in 2016.
Visit NGK Insulators at www.ngk.co.jp